Fatal error: Uncaught Error: Interface "TYPO3\CMS\Core\SingletonInterface" not found in /var/www/html/dev.hallescherfc.de/packages/muthsevmegamenu/Classes/Service/MegaMenuService.php:8 Stack trace: #0 {main} thrown in /var/www/html/dev.hallescherfc.de/packages/muthsevmegamenu/Classes/Service/MegaMenuService.php on line 8