Fatal error: Uncaught Error: Class "ilContainerReferenceXmlParser" not found in /var/www/html/ilias/components/ILIAS/GroupReference/classes/class.ilGroupReferenceXmlParser.php:15 Stack trace: #0 {main} thrown in /var/www/html/ilias/components/ILIAS/GroupReference/classes/class.ilGroupReferenceXmlParser.php on line 15