Thunar currently seems to crash when XDG_DATA_DIRS has a trailing or double colon. eg: export XDG_DATA_DIRS=$XDG_DATA_DIRS: This seems to be caused by a null path being returned on line 682 of thunar-vfs-mime-database.c. I'd try to fix it, but I'm deep into my exam period, and won't have time until the 27th.