Quitting neuro triggers uncaught exception in Ranvier websocket-networking

[stennie]

Expected behaviour: Quitting neuro should gracefully disconnect from Ranvier before shutting down.

Actual behaviour: Quitting neuro drops the connection and triggers an uncaught server exception due to lack of error handling in websocket-networking (which would be fixed via RanvierMUD/websocket-networking#2).

The onus should probably be on the server in this case, but Neuro could also call disconnect for a more graceful shutdown.