NullPointerException with nothing in your hand

Please attach the crash report.

I think a crash report is not required, Dinnerbone has already confirmed that..

https://twitter.com/IceTrailer/status/279219893117808641

But here:

http://hastebin.com/nepaheyiba.tex

In that case confirmed.

Confirmed also on OS X.

Crash report attached.

(NOTE: It STILL says "Is modded: Very likely; Jar signature invalidated" because I changed the default skin. No mods are installed.)

That's still a mod. (Even though it doesn't matter here).

It does not change any of the .class files of Minecraft.jar, just a texture.
That means it's not a mod.