Issue with certain users arrising.

Hey, a few of of our users accessing our quiz through Twitter are running into a 500 error after being redirected. Most Twitter users login just fine.

Here's the error backtrace: https://sentry.io/share/issue/06f9ada1027c46c88dc08b9df0dddde1/

And here's our app link: https://apps.twitter.com/app/13743569 