Fatal error: Uncaught Error: Call to a member function refinery() on null in /var/www/html/ilias/components/ILIAS/UI/src/examples/Tree/Expandable/expandable_async_repo.php:8 Stack trace: #0 {main} thrown in /var/www/html/ilias/components/ILIAS/UI/src/examples/Tree/Expandable/expandable_async_repo.php on line 8