Merge pull request #7186 in SW/shopware from ntr/5.5/fix-product-feed to 5.5

* commit '2039aed4e862c7e4bd5b3ded2d6a2d2d4e48d24c':
  NTR - Fix product feed saving

Author: soebbing

engine/Shopware/Models/ProductFeed/ProductFeed.php

@@ -1143,7 +1143,7 @@ public function sanitizeFilename()
         $this->fileName = basename($this->fileName);
         $extension = strtolower(pathinfo($this->fileName, PATHINFO_EXTENSION));
 
-        if (in_array($extension, \Shopware_Controllers_Backend_MediaManager::$fileUploadBlacklist, true)) {
+        if (!empty($extension) && in_array($extension, \Shopware_Controllers_Backend_MediaManager::$fileUploadBlacklist, true)) {
             $this->fileName = str_replace('.' . $extension, '.invalid', strtolower($this->fileName));
 
             // To prevent PrePersist event