Don't put local URI into thumbnail cache.

Author: dbrant

app/src/main/java/fr/free/nrw/commons/MediaWikiImageView.java

@@ -64,8 +64,10 @@ protected void onPostExecute(String result) {
             }
             if (TextUtils.isEmpty(result) && media.getLocalUri() != null) {
                 result = media.getLocalUri().toString();
+            } else {
+                // only cache meaningful thumbnails received from network.
+                CommonsApplication.getInstance().getThumbnailUrlCache().put(media.getFilename(), result);
             }
-            CommonsApplication.getInstance().getThumbnailUrlCache().put(media.getFilename(), result);
             setImageUrl(result);
         }
     }