Fatal error: Uncaught Error: Interface "ilAppEventListener" not found in /var/www/html/ilias/components/ILIAS/CourseReference/classes/class.ilCourseReferenceAppEventListener.php:8 Stack trace: #0 {main} thrown in /var/www/html/ilias/components/ILIAS/CourseReference/classes/class.ilCourseReferenceAppEventListener.php on line 8