When I click "Play" on my Minecraft Launcher, it crashes the game immediately.

Put the summary of the bug you're having here

What I expected to happen was...:
When I hit "Play", I expected for the game to start normally.

What actually happened was...:
The game immediately crashes and the development console reports a fatal error every time I click play, and it re-opens the launcher.

Steps to Reproduce:
1. Open the Minecraft Launcher version 1.4.4
2. ... Click "Play" after making sure you're using version 1.7.10 of Minecraft
3. ... It should crash there.