Check if response headers are empty in signin code

components/signin/core/browser/signin_header_helper.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 "components/signin/core/browser/signin_header_helper.h"
 
 #include <stddef.h>
 
 #include "base/macros.h"
 #include "base/strings/string_number_conversions.h"
@@ skipping 197 matching lines @@
 }
 
 ManageAccountsParams BuildManageAccountsParamsIfExists(net::URLRequest* request,
                                                        bool is_off_the_record) {
   ManageAccountsParams empty_params;
   empty_params.service_type = GAIA_SERVICE_TYPE_NONE;
   if (!gaia::IsGaiaSignonRealm(request->url().GetOrigin()))
     return empty_params;
 
   std::string header_value;
-  if (!request->response_headers()->GetNormalizedHeader(
+  net::HttpResponseHeaders* response_headers = request->response_headers();
+  if (!response_headers ||
+      !response_headers->GetNormalizedHeader(
           kChromeManageAccountsHeader, &header_value)) {
     return empty_params;
   }
 
   DCHECK(switches::IsEnableAccountConsistency() && !is_off_the_record);
   return BuildManageAccountsParams(header_value);
 }
 
 }  // namespace signin