simple.js crashes when slackroom settings are changed

[dunn]

It looks like the module itself has trouble handling events related to team/admin settings:

1. Create a bot through the Integrations page.
2. Add its API token to simple.js
3. node simple.js
4. Change (as far as I can tell) any admin setting—for example, add a custom username policy:

/Users/cat/Dropbox/projects/bots/slack/nerd/node_modules/slack-client/src/client.js:546
        return this.team.prefs[message.name] = message.value;
                                             ^
TypeError: Cannot set property 'username_policy' of undefined
    at Client.onMessage (/Users/cat/Dropbox/projects/bots/slack/nerd/node_modules/slack-client/src/client.js:546:46)
    at WebSocket.<anonymous> (/Users/cat/Dropbox/projects/bots/slack/nerd/node_modules/slack-client/src/client.js:142:24)
    at WebSocket.emit (events.js:98:17)
    at Receiver.self._receiver.ontext (/Users/cat/Dropbox/projects/bots/slack/nerd/node_modules/slack-client/node_modules/ws/lib/WebSocket.js:697:10)
    at Receiver.opcodes.1.finish (/Users/cat/Dropbox/projects/bots/slack/nerd/node_modules/slack-client/node_modules/ws/lib/Receiver.js:397:14)
    at Receiver.expectHandler (/Users/cat/Dropbox/projects/bots/slack/nerd/node_modules/slack-client/node_modules/ws/lib/Receiver.js:384:31)
    at Receiver.add (/Users/cat/Dropbox/projects/bots/slack/nerd/node_modules/slack-client/node_modules/ws/lib/Receiver.js:93:24)
    at CleartextStream.firstHandler (/Users/cat/Dropbox/projects/bots/slack/nerd/node_modules/slack-client/node_modules/ws/lib/WebSocket.js:678:22)
    at CleartextStream.emit (events.js:95:17)
    at CleartextStream.<anonymous> (_stream_readable.js:765:14)