First the error, if a player gets automatically kicked from the server for "No steam logon." ULib will print about 15 lines of this error:
[@ulib\shared\sh_ucl.lua:284] Tried to use a NULL entity!
From what I can see, when the user gets kicked he no longer has a "UniqueID" so you could just change the method that meta:GetUserGroup() calls that function, or another workaround.
Just figured I'd give you guys a heads up.
-hymsan