`http2client.c`: a 0-byte data frame is ok in message_body_forbidden cases.
This makes the check introduced in h2o/h2o#2971 slightly less strict.
@@ -470,7 +470,7 @@ static int handle_data_frame(struct st_h2o_http2client_conn_t *conn, h2o_http2_f
* All other responses do include a message body, although the body might
* be of zero length.
*/
- if (stream->input.message_body_forbidden) {
+ if (stream->input.message_body_forbidden && payload.length != 0) {
stream_send_error(conn, frame->stream_id, H2O_HTTP2_ERROR_PROTOCOL);
call_callback_with_error(stream, h2o_httpclient_error_protocol_violation);
close_stream(stream);
