ERR_NOMOTD is unhandled

[edef1c]

No 'motd' event is emitted on an ERR_NOMOTD.
This also causes initialisation to hang with a missing MOTD.
Possible resolutions:

• have a separate event for ERR_NOMOTD
  • upside: entirely unambiguous
  • downside: weird edge case (motd event is expected except in this weird edge case)
• .emit('motd', null)
  • upside: meaning is clear
  • downside: sort of a weird edge case (strings are expected except in this edge case)
• .emit('motd', '')
  • upside: everyone's code is ready to handle it (they already handle strings)
  • downside: meaning is less clear / conflicts with empty MOTD

[edef1c]

I pullreq'd both approaches. Pick one [=