Gallery.app : shows an error message when it fails to save an image.

ui/file_manager/gallery/js/gallery_item.js

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 /**
  * Object representing an image item (a photo).
  *
  * @param {!FileEntry} entry Image entry.
  * @param {!EntryLocation} locationInfo Entry location information.
  * @param {!MetadataItem} metadataItem
@@ skipping 288 matching lines @@
     }).then(function() {
       // Writes the blob of new image.
       return new Promise(function(fulfill, reject) {
         fileWriter.onerror = reject;
         fileWriter.onwriteend = fulfill;
         fileWriter.write(blob);
       });
     }).then(onSuccess.bind(null, fileEntry))
     .catch(function(error) {
       onError(error);
-      // Disable all callbacks on the first error.
-      fileWriter.onerror = null;
-      fileWriter.onwriteend = null;
+      if (fileWriter) {
+        // Disable all callbacks on the first error.
+        fileWriter.onerror = null;
+        fileWriter.onwriteend = null;
+      }
     });
   }.bind(this);
 
   var getFile = function(dir, newFile) {
     dir.getFile(name, {create: newFile, exclusive: newFile},
         function(fileEntry) {
           doSave(newFile, fileEntry);
         }.bind(this), onError);
   }.bind(this);
 
@@ skipping 51 matching lines @@
         return Promise.reject(str('GALLERY_FILE_EXISTS'));
       }, function() {
         return new Promise(
             this.entry_.moveTo.bind(this.entry_, parentDirectory, newFileName));
       }.bind(this));
     }.bind(this));
   }.bind(this)).then(function(entry) {
     this.entry_ = entry;
   }.bind(this));
 };