Wow. Looks as though you've really broken editing of (almost all membership) files manually.
Your gmod/settings/users.txt looks as though you've misplaced brackets and or quotes.
Though not required editing, ULib falls back on that.
According to the debug, you have no file, or data can't be read, or, the data is corrupt (again, most likely due to bracket or quote issues) of your gmod/data/ULib/groups.txt and users.txt