Fix error where twitter link on user profile showed just URL

If one signed in with one's GitHub account, the twitter handle would
not be set and therefore produce erroneous output.

![Screen Shot 2013-03-05 at 3 30 53 PM](https://f.cloud.github.com/assets/237985/221572/81c092d4-85a1-11e2-86d1-a93322173f3d.png)