failure on server

When @mtc2013 was testing we got this failure:

```
ubuntu@ip-172-31-35-239:~/async_slack_bot$ { type: 'message',
channel: 'D35B4MGCU',
user: 'U02B6JMJ6',
text: 'vote results',
ts: '1481754694.000008',
team: 'T0285CSTT',
event: 'direct_message',
match: [ 'vote', index: 0, input: 'vote results' ] }

/home/ubuntu/async_slack_bot/server.js:57
vote = message.text.match(/\d+/)[0]
^
TypeError: Cannot read property '0' of null
at Object.controller.hears.response (/home/ubuntu/async_slack_bot/server.js:57:35)
at Object. (/home/ubuntu/async_slack_bot/node_modules/botkit/lib/CoreBot.js:852:28)
at Object.Botkit.botkit.trigger (/home/ubuntu/async_slack_bot/node_modules/botkit/lib/CoreBot.js:879:49)
at Object. (/home/ubuntu/async_slack_bot/node_modules/botkit/lib/SlackBot.js:720:34)
at Object.Botkit.botkit.trigger (/home/ubuntu/async_slack_bot/node_modules/botkit/lib/CoreBot.js:879:49)
at /home/ubuntu/async_slack_bot/node_modules/botkit/lib/CoreBot.js:983:32
at Object.bot.findConversation (/home/ubuntu/async_slack_bot/node_modules/botkit/lib/Slackbot_worker.js:678:9)
at /home/ubuntu/async_slack_bot/node_modules/botkit/lib/CoreBot.js:979:21
at next (/home/ubuntu/async_slack_bot/node_modules/botkit/node_modules/ware/lib/index.js:82:27)
at Ware.run (/home/ubuntu/async_slack_bot/node_modules/botkit/node_modules/ware/lib/index.js:88:3)

```