diff --git a/plugins/calendar/drivers/kolab/kolab_calendar.php b/plugins/calendar/drivers/kolab/kolab_calendar.php
index ac7e9449..440d6e39 100644
--- a/plugins/calendar/drivers/kolab/kolab_calendar.php
+++ b/plugins/calendar/drivers/kolab/kolab_calendar.php
@@ -1,913 +1,913 @@
 <?php
 
 /**
  * Kolab calendar storage class
  *
  * @version @package_version@
  * @author Thomas Bruederli <bruederli@kolabsys.com>
  * @author Aleksander Machniak <machniak@kolabsys.com>
  *
  * Copyright (C) 2012-2015, Kolab Systems AG <contact@kolabsys.com>
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU Affero General Public License as
  * published by the Free Software Foundation, either version 3 of the
  * License, or (at your option) any later version.
  *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  * GNU Affero General Public License for more details.
  *
  * You should have received a copy of the GNU Affero General Public License
  * along with this program. If not, see <http://www.gnu.org/licenses/>.
  */
 
 
 class kolab_calendar extends kolab_storage_folder_api
 {
   public $ready = false;
   public $rights = 'lrs';
   public $editable = false;
   public $attachments = true;
   public $alarms = false;
   public $history = false;
   public $subscriptions = true;
   public $categories = array();
   public $storage;
 
   public $type = 'event';
 
   protected $cal;
   protected $events = array();
   protected $search_fields = array('title', 'description', 'location', 'attendees', 'categories');
 
   /**
    * Factory method to instantiate a kolab_calendar object
    *
    * @param string  Calendar ID (encoded IMAP folder name)
    * @param object  calendar plugin object
    * @return object kolab_calendar instance
    */
   public static function factory($id, $calendar)
   {
     $imap = $calendar->rc->get_storage();
     $imap_folder = kolab_storage::id_decode($id);
     $info = $imap->folder_info($imap_folder, true);
     if (empty($info) || $info['noselect'] || strpos(kolab_storage::folder_type($imap_folder), 'event') !== 0) {
       return new kolab_user_calendar($imap_folder, $calendar);
     }
     else {
       return new kolab_calendar($imap_folder, $calendar);
     }
   }
 
   /**
    * Default constructor
    */
   public function __construct($imap_folder, $calendar)
   {
     $this->cal = $calendar;
     $this->imap = $calendar->rc->get_storage();
     $this->name = $imap_folder;
 
     // ID is derrived from folder name
     $this->id = kolab_storage::folder_id($this->name, true);
     $old_id   = kolab_storage::folder_id($this->name, false);
 
     // fetch objects from the given IMAP folder
     $this->storage = kolab_storage::get_folder($this->name);
     $this->ready = $this->storage && $this->storage->valid;
 
     // Set writeable and alarms flags according to folder permissions
     if ($this->ready) {
       if ($this->storage->get_namespace() == 'personal') {
         $this->editable = true;
         $this->rights = 'lrswikxteav';
         $this->alarms = true;
       }
       else {
         $rights = $this->storage->get_myrights();
         if ($rights && !PEAR::isError($rights)) {
           $this->rights = $rights;
           if (strpos($rights, 't') !== false || strpos($rights, 'd') !== false)
             $this->editable = strpos($rights, 'i');;
         }
       }
       
       // user-specific alarms settings win
       $prefs = $this->cal->rc->config->get('kolab_calendars', array());
       if (isset($prefs[$this->id]['showalarms']))
         $this->alarms = $prefs[$this->id]['showalarms'];
       else if (isset($prefs[$old_id]['showalarms']))
         $this->alarms = $prefs[$old_id]['showalarms'];
     }
 
     $this->default = $this->storage->default;
     $this->subtype = $this->storage->subtype;
   }
 
 
   /**
    * Getter for the IMAP folder name
    *
    * @return string Name of the IMAP folder
    */
   public function get_realname()
   {
     return $this->name;
   }
 
   /**
    *
    */
   public function get_title()
   {
     return null;
   }
 
 
   /**
    * Return color to display this calendar
    */
   public function get_color($default = null)
   {
     // color is defined in folder METADATA
     if ($color = $this->storage->get_color()) {
       return $color;
     }
 
     // calendar color is stored in user prefs (temporary solution)
     $prefs = $this->cal->rc->config->get('kolab_calendars', array());
 
     if (!empty($prefs[$this->id]) && !empty($prefs[$this->id]['color']))
       return $prefs[$this->id]['color'];
 
     return $default ?: 'cc0000';
   }
 
   /**
    * Compose an URL for CalDAV access to this calendar (if configured)
    */
   public function get_caldav_url()
   {
     if ($template = $this->cal->rc->config->get('calendar_caldav_url', null)) {
       return strtr($template, array(
         '%h' => $_SERVER['HTTP_HOST'],
         '%u' => urlencode($this->cal->rc->get_user_name()),
         '%i' => urlencode($this->storage->get_uid()),
         '%n' => urlencode($this->name),
       ));
     }
 
     return false;
   }
 
 
   /**
    * Update properties of this calendar folder
    *
    * @see calendar_driver::edit_calendar()
    */
   public function update(&$prop)
   {
     $prop['oldname'] = $this->get_realname();
     $newfolder = kolab_storage::folder_update($prop);
 
     if ($newfolder === false) {
       $this->cal->last_error = $this->cal->gettext(kolab_storage::$last_error);
       return false;
     }
 
     // create ID
     return kolab_storage::folder_id($newfolder);
   }
 
   /**
    * Getter for a single event object
    */
   public function get_event($id)
   {
     // remove our occurrence identifier if it's there
     $master_id = preg_replace('/-\d{8}(T\d{6})?$/', '', $id);
 
     // directly access storage object
     if (!$this->events[$id] && $master_id == $id && ($record = $this->storage->get_object($id))) {
       $this->events[$id] = $this->_to_driver_event($record, true);
     }
 
     // maybe a recurring instance is requested
     if (!$this->events[$id] && $master_id != $id) {
       $instance_id = substr($id, strlen($master_id) + 1);
 
       if ($record = $this->storage->get_object($master_id)) {
         $master = $this->_to_driver_event($record);
       }
 
       if ($master) {
         // check for match in top-level exceptions (aka loose single occurrences)
         if ($master['_formatobj'] && ($instance = $master['_formatobj']->get_instance($instance_id))) {
           $this->events[$id] = $this->_to_driver_event($instance, false, true, $master);
         }
         // check for match on the first instance already
         else if ($master['_instance'] && $master['_instance'] == $instance_id) {
           $this->events[$id] = $master;
         }
         else if (is_array($master['recurrence'])) {
           // For performance reasons we'll get only the specific instance
           if (($date = substr($id, strlen($master_id) + 1, 8)) && strlen($date) == 8 && is_numeric($date)) {
             $start_date = new DateTime($date . 'T000000', $master['start']->getTimezone());
           }
 
           $this->get_recurring_events($record, $start_date ?: $master['start'], null, $id, 1);
         }
       }
     }
 
     return $this->events[$id];
   }
 
   /**
    * Get attachment body
    * @see calendar_driver::get_attachment_body()
    */
   public function get_attachment_body($id, $event)
   {
     if (!$this->ready)
         return false;
 
     $data = $this->storage->get_attachment($event['id'], $id);
 
     if ($data == null) {
         // try again with master UID
         $uid = preg_replace('/-\d+(T\d{6})?$/', '', $event['id']);
         if ($uid != $event['id']) {
             $data = $this->storage->get_attachment($uid, $id);
         }
     }
 
     return $data;
   }
 
   /**
    * @param  integer Event's new start (unix timestamp)
    * @param  integer Event's new end (unix timestamp)
    * @param  string  Search query (optional)
    * @param  boolean Include virtual events (optional)
    * @param  array   Additional parameters to query storage
    * @param  array   Additional query to filter events
    * @return array A list of event records
    */
   public function list_events($start, $end, $search = null, $virtual = 1, $query = array(), $filter_query = null)
   {
     // convert to DateTime for comparisons
     // #5190: make the range a little bit wider
     // to workaround possible timezone differences
     try {
       $start = new DateTime('@' . ($start - 12 * 3600));
     }
     catch (Exception $e) {
       $start = new DateTime('@0');
     }
     try {
       $end = new DateTime('@' . ($end + 12 * 3600));
     }
     catch (Exception $e) {
       $end = new DateTime('today +10 years');
     }
 
     // get email addresses of the current user
     $user_emails = $this->cal->get_user_emails();
 
     // query Kolab storage
     $query[] = array('dtstart', '<=', $end);
     $query[] = array('dtend',   '>=', $start);
 
     if (is_array($filter_query)) {
       $query = array_merge($query, $filter_query);
     }
 
     if (!empty($search)) {
         $search = mb_strtolower($search);
         $words = rcube_utils::tokenize_string($search, 1);
         foreach (rcube_utils::normalize_string($search, true) as $word) {
             $query[] = array('words', 'LIKE', $word);
         }
     }
     else {
       $words = array();
     }
 
     // set partstat filter to skip pending and declined invitations
     if (empty($filter_query) && $this->cal->rc->config->get('kolab_invitation_calendars')
       && $this->get_namespace() != 'other'
     ) {
       $partstat_exclude = array('NEEDS-ACTION','DECLINED');
     }
     else {
       $partstat_exclude = array();
     }
 
     $events = array();
     foreach ($this->storage->select($query) as $record) {
       $event = $this->_to_driver_event($record, !$virtual, false);
 
       // remember seen categories
       if ($event['categories']) {
         $cat = is_array($event['categories']) ? $event['categories'][0] : $event['categories'];
         $this->categories[$cat]++;
       }
 
       // list events in requested time window
       if ($event['start'] <= $end && $event['end'] >= $start) {
         unset($event['_attendees']);
         $add = true;
         // skip the first instance of a recurring event if listed in exdate
         if ($virtual && !empty($event['recurrence']['EXDATE'])) {
           $event_date = $event['start']->format('Ymd');
           $event_tz   = $event['start']->getTimezone();
 
           foreach ((array) $event['recurrence']['EXDATE'] as $exdate) {
             $ex = clone $exdate;
             $ex->setTimezone($event_tz);
 
             if ($ex->format('Ymd') == $event_date) {
               $add = false;
               break;
             }
           }
         }
 
         // find and merge exception for the first instance
         if ($virtual && !empty($event['recurrence']) && is_array($event['recurrence']['EXCEPTIONS'])) {
           foreach ($event['recurrence']['EXCEPTIONS'] as $exception) {
             if ($event['_instance'] == $exception['_instance']) {
               unset($exception['calendar'], $exception['className'], $exception['_folder_id']);
               // clone date objects from main event before adjusting them with exception data
               if (is_object($event['start'])) $event['start'] = clone $record['start'];
               if (is_object($event['end']))   $event['end']   = clone $record['end'];
               kolab_driver::merge_exception_data($event, $exception);
             }
           }
         }
 
         if ($add)
           $events[] = $event;
       }
 
       // resolve recurring events
       if ($record['recurrence'] && $virtual == 1) {
         $events = array_merge($events, $this->get_recurring_events($record, $start, $end));
       }
       // add top-level exceptions (aka loose single occurrences)
       else if (is_array($record['exceptions'])) {
         foreach ($record['exceptions'] as $ex) {
           $component = $this->_to_driver_event($ex, false, false, $record);
           if ($component['start'] <= $end && $component['end'] >= $start) {
             $events[] = $component;
           }
         }
       }
     }
 
     // post-filter all events by fulltext search and partstat values
     $me = $this;
     $events = array_filter($events, function($event) use ($words, $partstat_exclude, $user_emails, $me) {
       // fulltext search
       if (count($words)) {
         $hits = 0;
         foreach ($words as $word) {
           $hits += $me->fulltext_match($event, $word, false);
         }
         if ($hits < count($words)) {
           return false;
         }
       }
 
       // partstat filter
       if (count($partstat_exclude) && is_array($event['attendees'])) {
         foreach ($event['attendees'] as $attendee) {
           if (in_array($attendee['email'], $user_emails) && in_array($attendee['status'], $partstat_exclude)) {
             return false;
           }
         }
       }
 
       return true;
     });
 
     // Apply event-to-mail relations
     $config = kolab_storage_config::get_instance();
     $config->apply_links($events);
 
     // avoid session race conditions that will loose temporary subscriptions
     $this->cal->rc->session->nowrite = true;
 
     return $events;
   }
 
   /**
    * Get number of events in the given calendar
    *
    * @param  integer Date range start (unix timestamp)
    * @param  integer Date range end (unix timestamp)
    * @param  array   Additional query to filter events
    *
    * @return integer Count
    */
   public function count_events($start, $end = null, $filter_query = null)
   {
     // convert to DateTime for comparisons
     try {
       $start = new DateTime('@'.$start);
     }
     catch (Exception $e) {
       $start = new DateTime('@0');
     }
     if ($end) {
       try {
         $end = new DateTime('@'.$end);
       }
       catch (Exception $e) {
         $end = null;
       }
     }
 
     // query Kolab storage
     $query[] = array('dtend',   '>=', $start);
 
     if ($end)
       $query[] = array('dtstart', '<=', $end);
 
     // add query to exclude pending/declined invitations
     if (empty($filter_query)) {
       foreach ($this->cal->get_user_emails() as $email) {
         $query[] = array('tags', '!=', 'x-partstat:' . $email . ':needs-action');
         $query[] = array('tags', '!=', 'x-partstat:' . $email . ':declined');
       }
     }
     else if (is_array($filter_query)) {
       $query = array_merge($query, $filter_query);
     }
 
     // we rely the Kolab storage query (no post-filtering)
     return $this->storage->count($query);
   }
 
   /**
    * Create a new event record
    *
    * @see calendar_driver::new_event()
    *
    * @return mixed The created record ID on success, False on error
    */
   public function insert_event($event)
   {
     if (!is_array($event))
       return false;
 
     // email links are stored separately
     $links = $event['links'];
     unset($event['links']);
 
     //generate new event from RC input
     $object = $this->_from_driver_event($event);
     $saved  = $this->storage->save($object, 'event');
 
     if (!$saved) {
       rcube::raise_error(array(
         'code' => 600, 'type' => 'php',
         'file' => __FILE__, 'line' => __LINE__,
         'message' => "Error saving event object to Kolab server"),
         true, false);
       $saved = false;
     }
     else {
       // save links in configuration.relation object
       if ($this->save_links($event['uid'], $links)) {
         $object['links'] = $links;
       }
 
       $this->events = array($event['uid'] => $this->_to_driver_event($object, true));
     }
 
     return $saved;
   }
 
   /**
    * Update a specific event record
    *
    * @see calendar_driver::new_event()
    *
    * @return boolean True on success, False on error
    */
   public function update_event($event, $exception_id = null)
   {
     $updated = false;
     $old = $this->storage->get_object($event['uid'] ?: $event['id']);
     if (!$old || PEAR::isError($old))
       return false;
 
     // email links are stored separately
     $links = $event['links'];
     unset($event['links']);
 
     $object = $this->_from_driver_event($event, $old);
     $saved  = $this->storage->save($object, 'event', $old['uid']);
 
     if (!$saved) {
       rcube::raise_error(array(
         'code' => 600, 'type' => 'php',
         'file' => __FILE__, 'line' => __LINE__,
         'message' => "Error saving event object to Kolab server"),
         true, false);
     }
     else {
       // save links in configuration.relation object
       if ($this->save_links($event['uid'], $links)) {
         $object['links'] = $links;
       }
 
       $updated = true;
       $this->events = array($event['uid'] => $this->_to_driver_event($object, true));
 
       // refresh local cache with recurring instances
       if ($exception_id) {
         $this->get_recurring_events($object, $event['start'], $event['end'], $exception_id);
       }
     }
 
     return $updated;
   }
 
   /**
    * Delete an event record
    *
    * @see calendar_driver::remove_event()
    *
    * @return boolean True on success, False on error
    */
   public function delete_event($event, $force = true)
   {
     $deleted = $this->storage->delete($event['uid'] ?: $event['id'], $force);
 
     if (!$deleted) {
       rcube::raise_error(array(
           'code' => 600, 'file' => __FILE__, 'line' => __LINE__,
           'message' => sprintf("Error deleting event object '%s' from Kolab server", $event['id'])),
         true, false);
     }
 
     return $deleted;
   }
 
   /**
    * Restore deleted event record
    *
    * @see calendar_driver::undelete_event()
    *
    * @return boolean True on success, False on error
    */
   public function restore_event($event)
   {
     // Make sure this is not an instance identifier
     $uid = preg_replace('/-\d{8}(T\d{6})?$/', '', $event['id']);
 
     if ($this->storage->undelete($uid)) {
         return true;
     }
     else {
         rcube::raise_error(array(
           'code' => 600, 'file' => __FILE__, 'line' => __LINE__,
           'message' => sprintf("Error undeleting the event object '%s' from the Kolab server", $event['id'])),
         true, false);
     }
 
     return false;
   }
 
   /**
    * Find messages linked with an event
    */
   protected function get_links($uid)
   {
     $storage = kolab_storage_config::get_instance();
     return $storage->get_object_links($uid);
   }
 
   /**
    *
    */
   protected function save_links($uid, $links)
   {
     $storage = kolab_storage_config::get_instance();
     return $storage->save_object_links($uid, (array) $links);
   }
 
   /**
    * Create instances of a recurring event
    *
    * @param array    $event    Hash array with event properties
    * @param DateTime $start    Start date of the recurrence window
    * @param DateTime $end      End date of the recurrence window
    * @param string   $event_id ID of a specific recurring event instance
    * @param int      $limit    Max. number of instances to return
    *
    * @return array List of recurring event instances
    */
   public function get_recurring_events($event, $start, $end = null, $event_id = null, $limit = null)
   {
     $object = $event['_formatobj'];
     if (!$object) {
       $rec    = $this->storage->get_object($event['uid'] ?: $event['id']);
       $object = $rec['_formatobj'];
     }
 
     if (!is_object($object))
       return array();
 
     // determine a reasonable end date if none given
     if (!$end) {
       $end = clone $event['start'];
       $end->add(new DateInterval('P100Y'));
     }
 
     // copy the recurrence rule from the master event (to be used in the UI)
     $recurrence_rule = $event['recurrence'];
     unset($recurrence_rule['EXCEPTIONS'], $recurrence_rule['EXDATE']);
 
     // read recurrence exceptions first
     $events = array();
     $exdata = array();
     $futuredata = array();
     $recurrence_id_format = libcalendaring::recurrence_id_format($event);
 
     if (is_array($event['recurrence']['EXCEPTIONS'])) {
       foreach ($event['recurrence']['EXCEPTIONS'] as $exception) {
         if (!$exception['_instance'])
           $exception['_instance'] = libcalendaring::recurrence_instance_identifier($exception, $event['allday']);
 
         $rec_event = $this->_to_driver_event($exception, false, false, $event);
         $rec_event['id'] = $event['uid'] . '-' . $exception['_instance'];
         $rec_event['isexception'] = 1;
 
         // found the specifically requested instance: register exception (single occurrence wins)
         if ($rec_event['id'] == $event_id && (!$this->events[$event_id] || $this->events[$event_id]['thisandfuture'])) {
           $rec_event['recurrence'] = $recurrence_rule;
           $rec_event['recurrence_id'] = $event['uid'];
           $this->events[$rec_event['id']] = $rec_event;
         }
 
         // remember this exception's date
         $exdate = substr($exception['_instance'], 0, 8);
         if (!$exdata[$exdate] || $exdata[$exdate]['thisandfuture']) {
           $exdata[$exdate] = $rec_event;
         }
         if ($rec_event['thisandfuture']) {
           $futuredata[$exdate] = $rec_event;
         }
       }
     }
 
     // found the specifically requested instance, exiting...
     if ($event_id && !empty($this->events[$event_id])) {
       return array($this->events[$event_id]);
     }
 
     // Check first occurrence, it might have been moved
     if ($first = $exdata[$event['start']->format('Ymd')]) {
       // return it only if not already in the result, but in the requested period
       if (!($event['start'] <= $end && $event['end'] >= $start)
         && ($first['start'] <= $end && $first['end'] >= $start)
       ) {
           $events[] = $first;
       }
     }
 
     if ($limit && count($events) >= $limit) {
       return $events;
     }
 
     // use libkolab to compute recurring events
     $recurrence = new kolab_date_recurrence($object);
 
     $i = 0;
     while ($next_event = $recurrence->next_instance()) {
       $datestr     = $next_event['start']->format('Ymd');
       $instance_id = $next_event['start']->format($recurrence_id_format);
 
       // use this event data for future recurring instances
       if ($futuredata[$datestr])
         $overlay_data = $futuredata[$datestr];
 
       $rec_id      = $event['uid'] . '-' . $instance_id;
       $exception   = $exdata[$datestr] ?: $overlay_data;
       $event_start = $next_event['start'];
       $event_end   = $next_event['end'];
 
       // copy some event from exception to get proper start/end dates
       if ($exception) {
         $event_copy = $next_event;
         kolab_driver::merge_exception_dates($event_copy, $exception);
         $event_start = $event_copy['start'];
         $event_end   = $event_copy['end'];
       }
 
       // add to output if in range
       if (($event_start <= $end && $event_end >= $start) || ($event_id && $rec_id == $event_id)) {
         $rec_event = $this->_to_driver_event($next_event, false, false, $event);
         $rec_event['_instance'] = $instance_id;
         $rec_event['_count'] = $i + 1;
 
         if ($exception)  // copy data from exception
           kolab_driver::merge_exception_data($rec_event, $exception);
 
         $rec_event['id'] = $rec_id;
         $rec_event['recurrence_id'] = $event['uid'];
         $rec_event['recurrence'] = $recurrence_rule;
         unset($rec_event['_attendees']);
         $events[] = $rec_event;
 
         if ($rec_id == $event_id) {
           $this->events[$rec_id] = $rec_event;
           break;
         }
 
         if ($limit && count($events) >= $limit) {
           return $events;
         }
       }
       else if ($next_event['start'] > $end)  // stop loop if out of range
         break;
 
       // avoid endless recursion loops
       if (++$i > 100000)
           break;
     }
 
     return $events;
   }
 
   /**
    * Convert from Kolab_Format to internal representation
    */
   private function _to_driver_event($record, $noinst = false, $links = true, $master_event = null)
   {
     $record['calendar'] = $this->id;
 
     // remove (possibly outdated) cached parameters
     unset($record['_folder_id'], $record['className']);
 
     if ($links && !array_key_exists('links', $record)) {
       $record['links'] = $this->get_links($record['uid']);
     }
 
     $ns = $this->get_namespace();
 
     if ($ns == 'other') {
       $record['className'] = 'fc-event-ns-other';
     }
 
     if ($ns == 'other' || !$this->cal->rc->config->get('kolab_invitation_calendars')) {
       $record = kolab_driver::add_partstat_class($record, array('NEEDS-ACTION', 'DECLINED'), $this->get_owner());
 
       // Modify invitation status class name, when invitation calendars are disabled
       // we'll use opacity only for declined/needs-action events
       $record['className'] = str_replace('-invitation', '', $record['className']);
     }
 
     // add instance identifier to first occurrence (master event)
     $recurrence_id_format = libcalendaring::recurrence_id_format($master_event ? $master_event : $record);
     if (!$noinst && $record['recurrence'] && !$record['recurrence_id'] && !$record['_instance']) {
       $record['_instance'] = $record['start']->format($recurrence_id_format);
     }
     else if (is_a($record['recurrence_date'], 'DateTime')) {
       $record['_instance'] = $record['recurrence_date']->format($recurrence_id_format);
     }
 
     // clean up exception data
     if ($record['recurrence'] && is_array($record['recurrence']['EXCEPTIONS'])) {
       array_walk($record['recurrence']['EXCEPTIONS'], function(&$exception) {
         unset($exception['_mailbox'], $exception['_msguid'], $exception['_formatobj'], $exception['_attachments']);
       });
     }
 
     return $record;
   }
 
    /**
    * Convert the given event record into a data structure that can be passed to Kolab_Storage backend for saving
    * (opposite of self::_to_driver_event())
    */
   private function _from_driver_event($event, $old = array())
   {
     // set current user as ORGANIZER
     if ($identity = $this->cal->rc->user->list_emails(true)) {
       $event['attendees'] = (array) $event['attendees'];
       $found = false;
 
       // there can be only resources on attendees list (T1484)
       // let's check the existence of an organizer
       foreach ($event['attendees'] as $attendee) {
         if ($attendee['role'] == 'ORGANIZER') {
           $found = true;
           break;
         }
       }
 
       if (!$found) {
         $event['attendees'][] = array('role' => 'ORGANIZER', 'name' => $identity['name'], 'email' => $identity['email']);
       }
 
       $event['_owner'] = $identity['email'];
     }
 
     // remove EXDATE values if RDATE is given
     if (!empty($event['recurrence']['RDATE'])) {
       $event['recurrence']['EXDATE'] = array();
     }
 
     // remove recurrence information (e.g. EXDATES and EXCEPTIONS) entirely
     if ($event['recurrence'] && empty($event['recurrence']['FREQ']) && empty($event['recurrence']['RDATE'])) {
       $event['recurrence'] = array();
     }
 
     // keep 'comment' from initial itip invitation
     if (!empty($old['comment'])) {
       $event['comment'] = $old['comment'];
     }
 
     // remove some internal properties which should not be cached
     $cleanup_fn = function(&$event) {
       unset($event['_savemode'], $event['_fromcalendar'], $event['_identity'], $event['_folder_id'],
         $event['calendar'], $event['className'], $event['recurrence_id'],
-        $event['_attachments'], $event['attachments'], $event['deleted_attachments']);
+        $event['attachments'], $event['deleted_attachments']);
     };
 
     $cleanup_fn($event);
 
     // clean up exception data
     if (is_array($event['exceptions'])) {
       array_walk($event['exceptions'], function(&$exception) use ($cleanup_fn) {
         unset($exception['_mailbox'], $exception['_msguid'], $exception['_formatobj']);
         $cleanup_fn($exception);
       });
     }
 
     // copy meta data (starting with _) from old object
     foreach ((array)$old as $key => $val) {
       if (!isset($event[$key]) && $key[0] == '_')
         $event[$key] = $val;
     }
 
     return $event;
   }
 
   /**
    * Match the given word in the event contents
    */
   public function fulltext_match($event, $word, $recursive = true)
   {
     $hits = 0;
     foreach ($this->search_fields as $col) {
       $sval = is_array($event[$col]) ? self::_complex2string($event[$col]) : $event[$col];
       if (empty($sval))
         continue;
 
       // do a simple substring matching (to be improved)
       $val = mb_strtolower($sval);
       if (strpos($val, $word) !== false) {
         $hits++;
         break;
       }
     }
 
     return $hits;
   }
 
   /**
    * Convert a complex event attribute to a string value
    */
   private static function _complex2string($prop)
   {
       static $ignorekeys = array('role','status','rsvp');
 
       $out = '';
       if (is_array($prop)) {
           foreach ($prop as $key => $val) {
               if (is_numeric($key)) {
                   $out .= self::_complex2string($val);
               }
               else if (!in_array($key, $ignorekeys)) {
                 $out .= $val . ' ';
             }
           }
       }
       else if (is_string($prop) || is_numeric($prop)) {
           $out .= $prop . ' ';
       }
 
       return rtrim($out);
   }
 
 }