[SyncFS] Fix chrome://syncfs-internals callback handling

chrome/browser/ui/webui/sync_file_system_internals/extension_statuses_handler.cc

 // Copyright 2013 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/sync_file_system_internals/extension_statuses_handler.h"
 
 #include <map>
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
@@ skipping 63 matching lines @@
 }
 
 // static
 void ExtensionStatusesHandler::GetExtensionStatusesAsDictionary(
     Profile* profile,
     const base::Callback<void(const base::ListValue&)>& callback) {
   DCHECK(profile);
 
   sync_file_system::SyncFileSystemService* sync_service =
       SyncFileSystemServiceFactory::GetForProfile(profile);
-  if (!sync_service)
+  if (!sync_service) {
+    callback.Run(base::ListValue());
     return;
+  }
 
   ExtensionService* extension_service =
       extensions::ExtensionSystem::Get(profile)->extension_service();
-  if (!extension_service)
+  if (!extension_service) {
+    callback.Run(base::ListValue());
     return;
+  }
 
   sync_service->GetExtensionStatusMap(base::Bind(
       &ConvertExtensionStatusToDictionary,
       extension_service->AsWeakPtr(), callback));
 }
 
 void ExtensionStatusesHandler::GetExtensionStatuses(
     const base::ListValue* args) {
   DCHECK(args);
   GetExtensionStatusesAsDictionary(
       profile_,
       base::Bind(&ExtensionStatusesHandler::DidGetExtensionStatuses,
                  weak_ptr_factory_.GetWeakPtr()));
 }
 
 void ExtensionStatusesHandler::DidGetExtensionStatuses(
     const base::ListValue& list) {
   web_ui()->CallJavascriptFunction("ExtensionStatuses.onGetExtensionStatuses",
                                    list);
 }
 
 }  // namespace syncfs_internals