Fatal error: Uncaught Error: Class "ilBlockGUI" not found in /var/www/html/ilias/components/ILIAS/Calendar/classes/class.ilCalendarSelectionBlockGUI.php:30 Stack trace: #0 {main} thrown in /var/www/html/ilias/components/ILIAS/Calendar/classes/class.ilCalendarSelectionBlockGUI.php on line 30