Fix hanging errors

This is really two fixes, I'm sorry for mixing them into one.

The first fix is for some problems I have with my hubot, where it will sometimes "hang" on an error. this happens because the jabber-server restarts every night (Not really sure why, but it does..). Sometimes hubot connects at just the wrong moment and gets ECONNREFUSED, which leaves it just sitting there (the @error handler doesn't do anything). The second error I have seen is when the jabber server shuts down, hubot-xmpp sometimes hangs as well.

Both of the cases might be better handled with reconnection, but I couldn't figure out how to trigger that. If you have pointers, I'd be more than happy to change it :)

The second fix is to allow `robot.messageRoom` to work again. The envelope from that function has no `user` in it, to checking for type fails. I just added the `?` conditional to fall back to the group defaults.