Fixes for cr-settings-page-header

chrome/browser/resources/settings/settings_page/settings_page_header.js

 // Copyright 2015 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.
 
 /**
  * @fileoverview
  * 'cr-settings-page-header' shows a basic heading with a 'iron-icon'.
  *
  * Example:
  *
@@ skipping 52 matching lines @@
       computed: 'getCurrentPageTitle_(pageStack)',
     },
   },
 
   /**
    * @param {!Array<!HTMLElement>} pageStack
    * @return {string} The icon for the top page in the stack.
    * @private
    */
   getTopPageIcon_: function(pageStack) {
+    if (pageStack.length == 0)
+      return '';
     return pageStack[0].icon;
   },
 
   /**
    * @param {!HTMLElement} page
    * @return {string} A url link to the given page.
    * @private
    */
   urlFor_: function(page) {
     return page.route ? urlFor(page.route) : '';
   },
 
   /**
    * @param {!Array<!HTMLElement>} pageStack
    * @return {string} The title of the current page.
    * @private
    */
   getCurrentPageTitle_: function(pageStack) {
+    if (pageStack.length == 0)
+      return '';
     return pageStack[0].pageTitle;
   },
 
   /** @private */
   selectedPageChanged_: function() {
-    if (this.selectedPage.subpage) {
+    if (this.selectedPage && this.selectedPage.subpage) {
       // NOTE: Must reassign pageStack rather than doing push() so that the
       // computed property (parentPages) will be notified of the update.
       this.pageStack = this.pageStack.concat(this.selectedPage);
+    } else if (this.selectedPage) {
+      this.pageStack = [this.selectedPage];
     } else {
-      this.pageStack = [this.selectedPage];
+      this.pageStack = [];
     }
   },
 
   /**
    * Gets the parent pages in the given page stack; i.e. returns all pages but
    * the topmost subpage.
    *
    * @param {Array<HTMLElement>} stack
    * @return {!Array<HTMLElement>}
    * @private
    */
   getParentPages_: function(stack) {
     if (!stack || stack.length <= 1) {
       return [];
     }
 
     return stack.slice(0, stack.length - 1);
   },
 });