Guest mode causes certain settings to be hidden.

chrome/browser/resources/options/content_settings.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() {
   /** @const */ var Page = cr.ui.pageManager.Page;
   /** @const */ var PageManager = cr.ui.pageManager.PageManager;
 
   //////////////////////////////////////////////////////////////////////////////
   // ContentSettings class:
@@ skipping 166 matching lines @@
   ContentSettings.setHandlers = function(handlers) {
     $('handlers-list').setHandlers(handlers);
   };
 
   ContentSettings.setIgnoredHandlers = function(ignoredHandlers) {
     $('ignored-handlers-list').setHandlers(ignoredHandlers);
   };
 
   ContentSettings.setOTRExceptions = function(type, otrExceptions) {
     var exceptionsList = this.getExceptionsList(type, 'otr');
-    exceptionsList.parentNode.hidden = false;
-    exceptionsList.setExceptions(otrExceptions);
+    // Settings for Guest hides many sections, so check for null first.
+    if (exceptionsList) {
+      exceptionsList.parentNode.hidden = false;
+      exceptionsList.setExceptions(otrExceptions);
+    }
   };
 
   /**
    * @param {string} type The type of exceptions (e.g. "location") to get.
    * @param {string} mode The mode of the desired exceptions list (e.g. otr).
    * @return {?ExceptionsList} The corresponding exceptions list or null.
    */
   ContentSettings.getExceptionsList = function(type, mode) {
     return document.querySelector(
         'div[contentType=' + type + '] list[mode=' + mode + ']');
@@ skipping 102 matching lines @@
     var deviceSelect = $('media-select-camera');
     chrome.send('setDefaultCaptureDevice', ['camera', deviceSelect.value]);
   };
 
   // Export
   return {
     ContentSettings: ContentSettings
   };
 
 });