Fixed empty array for query result causing entity storage to crash loading a FALSE entity ID.

Closes #3444332

src/EntityUsageBatchManager.php

@@ -178,7 +178,7 @@ class EntityUsageBatchManager implements ContainerInjectionInterface {
       ->execute();
     $entity_id = reset($entity_ids);
 
-    if (isset($entity_id) && $entity = $entity_storage->load($entity_id)) {
+    if (!empty($entity_id) && $entity = $entity_storage->load($entity_id)) {
       /** @var \Drupal\Core\Entity\EntityInterface $entity */
       try {
         if ($entity->getEntityType()->isRevisionable()) {