Hammer Crashing When Opening the Material Browser

I’ve uploaded my dump file to metastruct, but I don’t understand what my issue is. http://dumps.metastruct.uk.to/dumper.py?dump=hammer_20161107_001146_1_crash.mdmp, I did add css material files to my gmod folder, but I’ve done it before and I’ve never had this issue. Is there anyways to reset my my materials folder without re-downloading gmod?

delete the material folder then verify game cache and gmod will just redownload the materials folder