Fatal error: Uncaught Error: Class 'Symfony\Contracts\EventDispatcher\Event' not found in /home/benjamincb/demos/acdg-site/vendor/contao/core-bundle/src/Event/PreviewUrlConvertEvent.php:19 Stack trace: #0 {main} thrown in /home/benjamincb/demos/acdg-site/vendor/contao/core-bundle/src/Event/PreviewUrlConvertEvent.php on line 19