fixed behavior with not loaded collection

Author: akaplya

app/code/Magento/Catalog/Model/ResourceModel/Product/Collection.php

@@ -2344,6 +2344,9 @@ public function addMediaGalleryData()
         if (!$this->getSize()) {
             return $this;
         }
+        if (!$this->isLoaded()) {
+            $this->load();
+        }
         $records = $this->getMediaGalleryResource()->getMediaRecords(
             $this->getStoreId(),
             $this->getLoadedIds()