ESP sending invalid error JSON response

[qiwzhang]

in gRPC transcoding case, somehow ESP is sending two cancated JSON.

{"status":"SERVING"}{
"code": 13,
"message": "HTTP/2 error code: INTERNAL_ERROR\nReceived Rst Stream",
"details": [
{
"@type": "type.googleapis.com/google.rpc.DebugInfo",
"stackEntries": [],
"detail": "internal"
}
]
}

I think if error happens in the middle of transcoding response. {"status": "SERVIING"} is from gRPC backend, then RST is received. ESP appended another JSON status in the response body.