Add bracket guards around ifs
Merge branch 'master' of git://ahi.cs.unc.edu/pavel/FasTC
Don't crash when you can't open a file that doesn't exist
Lots of QOL fixes:

1. Avoid the need for multiple-of-four input textures. If you don't pass
a multiple of four then we'll do our best to pad the image.

2. Fix a bunch of bugs where we didn't accurately report why we couldn't
compress a texture and just crashed instead.

3. Some code refactoring to make certain if statements more readable.