PHP versions not loaded in Subdomain/Alias Vhost with PHP-FPM as Default PHP Handler

Summary

When I have PHP-FPM as default PHP Handler, the PHP versions are not loaded in the create form for Subdomain Vhost interface and Alias Vhost interface. If I switch to PHP Handler "Disabled" and switch back to "PHP-FPM", the PHP version is refreshing, and now I get the PHP version.

It looks like PHP version list is not loaded when the form is opened, and only relies on PHP Handler selection change events to reload it.

Steps to reproduce

1. System > Main Config (under Interface section) > enable Create subdomains as web site (or Create aliasdomains as web site as you wish) and Save.
2. System > Server Config (under System section) > (your server hostname) > Web tab > set Default PHP Handler to PHP-FPM (under PHP Settings section) and Save.
3. Sites > Subdomain (Vhost) (under Websites section) (or Aliasdomain (Vhost) as you wish) > Add new subdomain (or Add new aliasdomain as you wish).
4. See the PHP version dropdown being empty.

Correct behaviour

The PHP version dropdown should be filled when the form is loaded if the Default PHP Handler allows custom PHP version (FastCGI or PHP-FPM).

Environment

Server OS + version: Debian 11 ISPConfig version: 3.2.12p1