[DevTools] Fix crash in DevToolsWindow::Create

chrome/browser/ui/apps/chrome_app_window_client.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/apps/chrome_app_window_client.h"
 
 #include "base/memory/singleton.h"
 #include "chrome/browser/apps/scoped_keep_alive.h"
 #include "chrome/browser/devtools/devtools_window.h"
 #include "chrome/common/extensions/features/feature_channel.h"
@@ skipping 39 matching lines @@
 #else
   return CreateNativeAppWindowImpl(window, *params);
 #endif
 }
 
 void ChromeAppWindowClient::OpenDevToolsWindow(
     content::WebContents* web_contents,
     const base::Closure& callback) {
   DevToolsWindow* devtools_window = DevToolsWindow::OpenDevToolsWindow(
       web_contents, DevToolsToggleAction::ShowConsole());
-  devtools_window->SetLoadCompletedCallback(callback);
+  if (devtools_window) {
+    devtools_window->SetLoadCompletedCallback(callback);
+  } else {
+   callback.Run();
+  }
 }
 
 bool ChromeAppWindowClient::IsCurrentChannelOlderThanDev() {
   return extensions::GetCurrentChannel() > chrome::VersionInfo::CHANNEL_DEV;
 }