Module core v12.0.45 page.ampusers.php missing variable

Hello,

Recently I noticed that I am unable to operate in the Admin -> Administrators section of the web interface.
For example if I want to modify an admin account, I am redirected to http://<mypbxurl>/admin/config.php?display=&userdisplay=snikolov

That just loads the system status page.
I managed to fix the issue locally, by defining

$display = ampusers;

somewhere in the beginning of
/var/www/html/admin/modules/core/page.ampusers.php

Now the HTTP GET looks correct and the module is working:
http://<mypbxurl>/admin/config.php?display=ampusers&userdisplay=snikolov

Please fix it officially.

Kind regards,
Stefan Nikolov