Fixed JS Console Error in the Wallpaper Picker App when selecting a custom wallpaper

chrome/browser/resources/chromeos/wallpaper_manager/js/wallpaper_manager.js

 // Copyright (c) 2013 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.
 
 /**
  * WallpaperManager constructor.
  *
  * WallpaperManager objects encapsulate the functionality of the wallpaper
  * manager extension.
  *
@@ skipping 599 matching lines @@
 
   /**
    * Set attributions of wallpaper with given URL. If URL is not valid, clear
    * the attributions.
    * @param {{baseURL: string, dynamicURL: string, layout: string,
    *          author: string, authorWebsite: string, availableOffline: boolean}}
    *     selectedItem selected wallpaper item in grid.
    * @private
    */
   WallpaperManager.prototype.setWallpaperAttribution_ = function(selectedItem) {
-    if (selectedItem) {
+    if (selectedItem && selectedItem.source != 'ADDNEW') {
       $('author-name').textContent = selectedItem.author;
       $('author-website').textContent = $('author-website').href =
           selectedItem.authorWebsite;
       chrome.wallpaperPrivate.getThumbnail(selectedItem.baseURL,
                                            selectedItem.source,
                                            function(data) {
         var img = $('attribute-image');
         if (data) {
           var blob = new Blob([new Int8Array(data)], {'type' : 'image\/png'});
           img.src = window.URL.createObjectURL(blob);
@@ skipping 375 matching lines @@
           }
         }
       }
       this.wallpaperGrid_.dataModel = wallpapersDataModel;
       this.wallpaperGrid_.selectedItem = selectedItem;
       this.wallpaperGrid_.activeItem = selectedItem;
     }
   };
 
 })();