Ubuntu 22 provisioning error in netplan config

Problem: netplan config error, then provisioning crashes

Foreman and Proxy versions: 3.10.0 with Katello 4.12.0

Other relevant data:
The templates preseed_netplan_xxx configures the network in the autoinstall.yaml file at the beginning of the PXE installation process. But it sets “dhcp6: null” instead of “dhcp6: false” and it crashes the process.
I tryed to edit the snippet “preseed_netplan_generic_interface”, replacing the line “dhcp6: <%= @dhcp6 %>” by “dhcp6: false” and it worked.
Did I miss something about dhcp6 configuration or is this a bug ?
I think the problem appears since I update to 3.10/4.12.

Regards,
JF