Optimize INSERT query to avoid an extra UPDATE

BaseEntityPersister can save an extra UPDATE query when it
persists a self-referencing entity using an application
generated identifier

Fixes doctrine#7877

lib/Doctrine/ORM/Persisters/Entity/BasicEntityPersister.php

@@ -650,6 +650,7 @@ protected function prepareUpdateData($entity)
                     // The associated entity $newVal is not yet persisted, so we must
                     // set $newVal = null, in order to insert a null value and schedule an
                     // extra update on the UnitOfWork.
+
                     $uow->scheduleExtraUpdate($entity, [$field => [null, $newVal]]);
 
                     $newVal = null;