MAGETWO-55447: Portdown MAGETWO-54718 down to M2.1.x branch

- MAGETWO-54718: [GitHub] Exception thrown where no Product Image file found #5184 #5497 #5871

- (cherry picked from commit 0bad8ab)

Author: andimov

app/code/Magento/Catalog/Block/Adminhtml/Product/Helper/Form/Gallery/Content.php

@@ -134,7 +134,7 @@ public function getImagesJson()
             is_array($value['images']) &&
             count($value['images'])
         ) {
-            $mediaDir = $this->_filesystem->getDirectoryRead(DirectoryList::MEDIA);            
+            $mediaDir = $this->_filesystem->getDirectoryRead(DirectoryList::MEDIA);
             $images = $this->sortImagesByPosition($value['images']);
             foreach ($images as &$image) {
                 $image['url'] = $this->_mediaConfig->getMediaUrl($image['file']);