Issue #2981825 by jorgvloet: Notice: Undefined index: revision_id and Notice:...

Issue #2981825 by jorgvloet: Notice: Undefined index: revision_id and Notice: Undefined index: rev_id_current when exporting custom blocks

src/Controller/BlocksController.php

@@ -65,6 +65,8 @@ public function exportBlocks(array $form = NULL, FormStateInterface $form_state
         'langcode' => $block->langcode->getValue()[0]['value'],
         'uuid' => $block->uuid(),
         'bundle' => $block->bundle(),
+        'revision_id' => null,
+        'rev_id_current' => null,
       ];
 
       $entityFieldManager = StructureSyncHelper::getEntityFieldManager();