Merge to M54: Check if response headers are empty in signin code

components/signin/core/browser/signin_header_helper.cc

Index: components/signin/core/browser/signin_header_helper.cc
diff --git a/components/signin/core/browser/signin_header_helper.cc b/components/signin/core/browser/signin_header_helper.cc
index 578cb5806cf889ec323d359d175515b17120ffdd..8e946af395969f323286aa0bda98fad78963cc6a 100644
--- a/components/signin/core/browser/signin_header_helper.cc
+++ b/components/signin/core/browser/signin_header_helper.cc
@@ -215,7 +215,9 @@ ManageAccountsParams BuildManageAccountsParamsIfExists(net::URLRequest* request,
     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;
   }