diff --git a/lib/kolab_sync.php b/lib/kolab_sync.php
--- a/lib/kolab_sync.php
+++ b/lib/kolab_sync.php
@@ -45,6 +45,8 @@
     public $username;
     public $password;
 
+    public $task = null;
+
     const CHARSET = 'UTF-8';
     const VERSION = "2.3.22";
 
@@ -207,7 +209,7 @@
             }
 
             // LDAP server failure... send 503 error
-            if ($auth['kolab_ldap_error']) {
+            if ($auth['kolab_ldap_error'] ?? null) {
                 self::server_error();
             }
 
@@ -223,7 +225,7 @@
         }
 
         // Authenticate - get Roundcube user ID
-        if (!$auth['abort'] && ($userid = $this->login($auth['user'], $auth['pass'], $auth['host'], $err))) {
+        if (!($auth['abort'] ?? false) && ($userid = $this->login($auth['user'], $auth['pass'], $auth['host'], $err))) {
             // set real username
             $this->username = $auth['user'];
             return $userid;
@@ -298,6 +300,7 @@
 
         // parse $host
         $a_host = parse_url($host);
+        $port = null;
         if ($a_host['host']) {
             $host = $a_host['host'];
             $ssl = (isset($a_host['scheme']) && in_array($a_host['scheme'], array('ssl','imaps','tls'))) ? $a_host['scheme'] : null;