Merge pull request #17 from vatasik/master

change ElasticTableGateway.php check id from isset to !empty

Author: Indigerd

src/TableGateway/ElasticTableGateway.php

@@ -60,7 +60,7 @@ public function insert(array $data, array $options = []): ?array
             $this->collectionName,
             $this->documentType,
             $data,
-            (isset($id) ? $id : null),
+            (!empty($id) ? $id : null),
             $options
         );
         return ['_id' => $result['_id']];