Occasional mysterious shader crash

[nusgart]

Occasionally, caligula crashes with a strange shader syntax error that is not present in the file. I suspect that this has been caused by a null pointer deference that I recently added code to guard against but this has not been confirmed as the issue is rare.

[gregjohnson2017]

Can no longer confirm that this bug still occurs, has not happened in a very long time.

[nusgart]

We should probably do a git bisect and figure out whether we actually fixed this and how