Damn! I knew I forgot something!
The error is possibly occurring because there is no sort defined in your configuration variable. If you change the
code:
U_Username-Username-U-10|
to
code:
U_Username-Username-A-10|
it should work. I will add a new check to ensure that if there is no sort, the first field will always allow the sorts.
I am working on an updated version since (now that I am fully awake

) I haven't put checks if the Username exists in the configuration script, which is essential for the Userlist Sort modification.
I have updated the files on the first post.
Warm regards
Nikos