Verify that we correctly handle an invalid itip messages
Triggers:
PHP Error: iCal data parse error: Object validation failed: missing mandatory object properties in \/opt\/app-root\/src\/roundcubemail\/plugins\/libcalendaring\/lib\/libcalendaring_vcalendar.php on line 165 (POST \/?Cmd=Sync&User=john@kolab.org&DeviceId=test1712766482&DeviceType=WindowsOutlook15)"