Error when i add something on the calendar

[ghost]

Hello when i m trying to add something on calendar i have the error :

error  Tue, 21 Apr 2015 08:42:20 +0200  php
Trying to get property of non-object (/var/www/humhub/protected/modules/calendar/models/CalendarEntry.php:340) Stack trace: #0 /var/www/humhub/protected/vendors/yii/db/ar/CActiveFinder.php(167): CJoinElement->afterFind() #1 /var/www/humhub/protected/vendors/yii/db/ar/CActiveRecord.php(281): CActiveFinder->lazyFind() #2 /var/www/humhub/protected/vendors/yii/db/ar/CActiveRecord.php(143): CalendarEntryParticipant->getRelated() #3 /var/www/humhub/protected/modules/calendar/models/CalendarEntryParticipant.php(108): CalendarEntryParticipant->__get() #4 /var/www/humhub/protected/vendors/yii/db/ar/CActiveRecord.php(1097): CalendarEntryParticipant->afterSave() #5 /var/www/humhub/protected/vendors/yii/db/ar/CActiveRecord.php(806): CalendarEntryParticipant->insert() #6 /var/www/humhub/protected/modules/calendar/models/CalendarEntry.php(382): CalendarEntryParticipant->save() #7 /var/www/humhub/protected/vendors/yii/db/ar/CActiveRecord.php(1097): CalendarEntry->afterSave() #8 /var/www/humhub/protected/vendors/yii/db/ar/CActiveRecord.php(806): CalendarEntry->insert() #9 /var/www/humhub/protected/modules/calendar/controllers/EntryController.php(157): CalendarEntry->save() #10 /var/www/humhub/protected/vendors/yii/web/actions/CInlineAction.php(49): EntryController->actionEdit() #11 /var/www/humhub/protected/vendors/yii/web/CController.php(308): CInlineAction->runWithParams() #12 /var/www/humhub/protected/vendors/yii/web/filters/CFilterChain.php(133): EntryController->runAction() #13 /var/www/humhub/protected/vendors/yii/web/filters/CFilter.php(40): CFilterChain->run() #14 /var/www/humhub/protected/vendors/yii/web/CController.php(1145): CAccessControlFilter->filter() #15 /var/www/humhub/protected/vendors/yii/web/filters/CInlineFilter.php(58): EntryController->filterAccessControl() #16 /var/www/humhub/protected/vendors/yii/web/filters/CFilterChain.php(130): CInlineFilter->filter() #17 /var/www/humhub/protected/vendors/yii/web/CController.php(291): CFilterChain->run() #18 /var/www/humhub/protected/vendors/yii/web/CController.php(265): EntryController->runActionWithFilters() #19 /var/www/humhub/protected/vendors/yii/web/CWebApplication.php(282): EntryController->run() #20 /var/www/humhub/protected/vendors/yii/web/CWebApplication.php(141): WebApplication->runController() #21 /var/www/humhub/protected/vendors/yii/base/CApplication.php(180): WebApplication->processRequest() #22 /var/www/humhub/index.php(39): WebApplication->run() REQUEST_URI=/humhub/index.php?r=calendar/entry/edit&id=&sguid=acdabead-5a33-4e4f-b8b4-57923f972ad2 in /var/www/humhub/protected/modules/calendar/models/CalendarEntry.php (340) in /var/www/humhub/protected/modules/calendar/models/CalendarEntryParticipant.php (108) in /var/www/humhub/protected/modules/calendar/models/CalendarEntry.php (382) in /var/www/humhub/protected/modules/calendar/controllers/EntryController.php (157) in /var/www/humhub/index.php (39)
warning  Tue, 21 Apr 2015 08:42:20 +0200  application
Failed to set unsafe attribute "selected_participants" of "CalendarEntry". in /var/www/humhub/protected/modules/calendar/controllers/EntryController.php (143) in /var/www/humhub/index.php (39)

how fix taht please

[chezmix]

Same thing happened to me once but I couldn't replicate it again afterwards.