Fix a browser crash on opening 'chrome://voicesearch' in guest mode.

chrome/browser/ui/webui/voicesearch_ui.cc

 // 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.
 
 #include "chrome/browser/ui/webui/voicesearch_ui.h"
 
 #include "base/command_line.h"
 #include "base/metrics/field_trial.h"
 #include "base/path_service.h"
 #include "base/prefs/pref_service.h"
@@ skipping 227 matching lines @@
   void AddHotwordInfo(base::ListValue* list)  {
     std::string search_enabled = "No";
     if (profile_->GetPrefs()->GetBoolean(prefs::kHotwordSearchEnabled))
       search_enabled = "Yes";
     AddPair(list, ASCIIToUTF16("Hotword Search Enabled"),
             ASCIIToUTF16(search_enabled));
 
     std::string audio_logging_enabled = "No";
     HotwordService* hotword_service =
         HotwordServiceFactory::GetForProfile(profile_);
-    if (hotword_service->IsOptedIntoAudioLogging())
+    if (hotword_service && hotword_service->IsOptedIntoAudioLogging())
       audio_logging_enabled = "Yes";
     AddPair(list, ASCIIToUTF16("Hotword Audio Logging Enabled"),
             ASCIIToUTF16(audio_logging_enabled));
 
     std::string group = base::FieldTrialList::FindFullName(
         hotword_internal::kHotwordFieldTrialName);
     AddPair(list, ASCIIToUTF16("Field trial"), ASCIIToUTF16(group));
 
     AddLineBreak(list);
   }
@@ skipping 105 matching lines @@
 VoiceSearchUI::VoiceSearchUI(content::WebUI* web_ui)
     : content::WebUIController(web_ui) {
   Profile* profile = Profile::FromWebUI(web_ui);
   web_ui->AddMessageHandler(new VoiceSearchDomHandler(profile));
 
   // Set up the about:voicesearch source.
   content::WebUIDataSource::Add(profile, CreateVoiceSearchUiHtmlSource());
 }
 
 VoiceSearchUI::~VoiceSearchUI() {}