adding empty method stub for missing image function

Classes/ViewHelper/Form/UploadViewHelper.php

@@ -86,4 +86,9 @@ class UploadViewHelper extends CoreUploadViewHelper
         }
         return $this->propertyMapper->convert($resource, FileReference::class);
     }
+
+    private function getValue($param){
+        //TODO
+        return null;
+    }
 }