Comment 35 for bug 691653

Well, this is a pretty simpleminded check, but it looks like it might prevent it from crashing at least.

Still doesn't answer why the null pointer got in there to begin with.

We've got a new mesa release coming soon. I poked through the git tree looking for an obvious fix for this issue but didn't spot it. Still, I think the next step would be to test a newer mesa to verify it still has this bug, and then test out if this patch solves it, or just shifts the issue to some other bit of code. (Guessing the latter).