Fix overlay display in certificate options.

chrome/browser/resources/options2/options_page.js

 // Copyright (c) 2012 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.
 
 cr.define('options', function() {
   /////////////////////////////////////////////////////////////////////////////
   // OptionsPage class:
 
   /**
    * Base class for options page.
@@ skipping 761 matching lines @@
      * @private
      */
     setOverlayVisible_: function(visible) {
       assert(this.isOverlay);
       var pageDiv = this.pageDiv;
       var container = this.container;
 
       if (visible) {
         uber.invokeMethodOnParent('beginInterceptingEvents');
         this.pageDiv.removeAttribute('aria-hidden');
-        this.parentPage.pageDiv.setAttribute('aria-hidden', true);
+        if (this.parentPage)
+          this.parentPage.pageDiv.setAttribute('aria-hidden', true);
       } else {
-        this.parentPage.pageDiv.removeAttribute('aria-hidden');
+        if (this.parentPage)
+          this.parentPage.pageDiv.removeAttribute('aria-hidden');
       }
 
       if (container.hidden != visible) {
         if (visible) {
           // If the container is set hidden and then immediately set visible
           // again, the fadeCompleted_ callback would cause it to be erroneously
           // hidden again. Removing the transparent tag avoids that.
           container.classList.remove('transparent');
 
           // Hide all dialogs in this container since a different one may have
@@ skipping 102 matching lines @@
     canShowPage: function() {
       return true;
     },
   };
 
   // Export
   return {
     OptionsPage: OptionsPage
   };
 });