Fresh install of both backdrop and CiviCRM on Deb 12. When creating a user, I'm receiving the following:
Fresh install on backdrop and receiving a similar message:
_civicrm_group_roles_validate_groups(): Argument #1 ($group_ids) must be of type array, null given, called in /var/www/backdrop/modules/civicrm/backdrop/modules/civicrm_group_roles/civicrm_group_roles.module on line 108
Advice is welcomed
Welcome Larry! I think you found a compatibility issue with PHP 8. Those have mostly been stamped out for a while, but I think you found a case that folks haven't uncovered yet.
I just wrote a patch here: https://github.com/civicrm/civicrm-backdrop/pull/173. Could you please install it and report back if it fixes the issue? If you're not sure how to apply the patch, please leave a comment on this answer and I can give you more detailed instructions.
