Fix null metadata dereference in Thrift proxy router for shadow traffic#38181

zuercher merged 4 commits intoenvoyproxy:mainenvoyproxy/envoy:mainfrom

PeterL328:yleng/fix_crash_with_thrift_proxy_null_response_metadata_for_shadowPeterL328/envoy:yleng/fix_crash_with_thrift_proxy_null_response_metadata_for_shadowCopy head branch name to clipboard