I've the same problem with new installation of CiviCRM in Backdrop on my own Debian 12 machine:
array_keys(): Argument #1 ($array) must be of type array, null given
when trying to set up a Association Rule for matching CiviCRM Group Administrators to Backdrop Role Administrator.
In the log nothing more IMO:
TypeError: array_keys(): Argument #1 ($array) must be of type array, null given in array_keys() (line 586 of /var/www/html/backdrop/modules/civicrm/backdrop/modules/civicrm_group_roles/civicrm_group_roles.module).
Backdrop CMS: 1.26.2 PHP Version: 8.2.7 CiviCRM: 5.67.3