Range deploy failing with template error on Debian 13 / Proxmox 9

After upgrading an existing Ludus installation to Debian 13 and Proxmox 9, range deploy commands fail with:

TASK [Modify router firewall to allow WireGuard IP's for access grants to this range] ***
[ERROR]: The filter plugin 'ansible.builtin.list' failed: 'NoneType' object is not iterable
Origin: /opt/ludus/ansible/range-management/tasks/firewall/set-firewall-rules.yml:102:9
loop: "{{ range_access_grants_array | default([]) | list }}"

Modifying lines 86-88 in /ludus-server/ansible/range-management/tasks/firewall/set-firewall-rules as follows:

- name: Set range_access_grants_array from access_grants_array
  ansible.builtin.set_fact:
    range_access_grants_array: "{{ access_grants_array | default([], true) }}"

seems to fix the problem. Not sure if it was related to package changes in the Debian 13 upgrade, but posting here in case it can help someone else.