message: Fix client build
diff: @@ -89,7 +89,7 @@ fn process_loop(
  return state;
  }
  - let (out_dgrams, _timer) = client.process(&[], now());
  + let (out_dgrams, _timer) = client.process(vec![], now());
  emit_packets(&socket, &out_dgrams);
  let sz = socket.recv(&mut buf[..]).expect("UDP error");
  