Issue #3304728 by kristiaanvandeneynde: Add member page missing due to...

Issue #3304728 by kristiaanvandeneynde: Add member page missing due to operation not being supported

Closes #3478088

src/Entity/GroupRelationship.php

@@ -263,7 +263,7 @@ class GroupRelationship extends ContentEntityBase implements GroupRelationshipIn
       // flush some caches containing the entity or perform other operations we
       // cannot possibly know about. Lucky for us, all of that behavior usually
       // happens when saving an entity so let's re-save the added entity.
-      $this->getEntity()->save();
+      $this->getEntity()->setSyncing(TRUE)->save();
     }
 
     // If a membership gets updated, but the member's roles haven't changed, we
@@ -300,6 +300,7 @@ class GroupRelationship extends ContentEntityBase implements GroupRelationshipIn
         // trying to save an entity that just got deleted and triggered the
         // deletion of its relationship entities.
         // @todo Revisit when https://www.drupal.org/node/2754399 lands.
+        $entity->setSyncing(TRUE);        
         $entity->save();
 
         // If a membership gets deleted, we need to reset the internal group