Response closed without grpc-status

### Problem description
I used improbable-eng/grpc-web to generate the stub codes and using in angular app. I can connect to the grpc-js server successfully. In addition, an Envoy proxy is introducted between them for ensuring h2 stream transport. The server could steady push messages to the client. However, the connection might be interrupted because of this error `Response closed without grpc-status`.
It looks like that the header `grpc-status` for current push wasn't be set. I have no idea whether the envoy is the reason or the grpc server.
I tried to enable all Tracers and DEBUG severity. Unfortuantely I can not see anything details about the request and response headers.

### Reproduction steps
A simple grpc server keeps connection alive and push messages every minutes. The error occurs about every 5 minutes.

### Environment
- OS version: Windows 10 WSL: Ubuntu x64
- Node version: v12.14.1
- Node installation method: nvm
- Package name and version: grpc@1.24.2 or @grpc/grpc-js@0.7.3

### Additional context
I'll later further check with grpc-node client, also the envoy logs. If someone knows more about this error, please let me know.