Fatal error: Uncaught Error: Class 'Drupal\Core\Field\EntityReferenceFieldItemList' not found in /var/www/html/tmp/contrib/flag/src/Plugin/Field/FlaggedEntityFieldItemList.php:11 Stack trace: #0 {main} thrown in /var/www/html/tmp/contrib/flag/src/Plugin/Field/FlaggedEntityFieldItemList.php on line 11