Add extra size check to avoid unwanted Seg Fault

headless/public/util/generic_url_request_job.cc

Index: headless/public/util/generic_url_request_job.cc
diff --git a/headless/public/util/generic_url_request_job.cc b/headless/public/util/generic_url_request_job.cc
index 4cf9bdd257cff27157b88b9279bd6988f9b5083d..779f74461769a649f4d991456408d2ae5f36bf2a 100644
--- a/headless/public/util/generic_url_request_job.cc
+++ b/headless/public/util/generic_url_request_job.cc
@@ -276,6 +276,9 @@ std::string GenericURLRequestJob::GetPostData() const {
   if (!stream->GetElementReaders())
     return "";
 
+  if (stream->GetElementReaders()->size() == 0)
+    return "";
+
   DCHECK_EQ(1u, stream->GetElementReaders()->size());
   const net::UploadBytesElementReader* reader =
       (*stream->GetElementReaders())[0]->AsBytesReader();