Client does not handle router disconnection correctly

[Mahad-10]

Steps to reproduce:

1. Start a nxt router.
2. Subscribe to a topic test on a new terminal.
3. Disconnect the router.

The error logs for client:

maddy@office-pc:~$ wick subscribe test
[INFO] Press Ctrl+C to exit
[INFO] Subscribed to topic 'test'

thread 'tokio-runtime-worker' (14120) panicked at /root/.cargo/git/checkouts/xconn-rust-6691396e6216d75d/2bf55ac/src/async_/websocket.rs:28:48:
called `Result::unwrap()` on an `Err` value: Protocol(ResetWithoutClosingHandshake)
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
^C[INFO] Exiting...
[ERROR] Session 1 Error leaving: failed to send message: write error: Trying to work with closed connection