By coincidence, both template types that we have in core have operatingsystems association, so the form renders properly for them. Other templates that are added from plugins that do not have this association, therefore an error occurs when rendering the form. We should check whether the method is defined first. The breaking change was introduced in 1.10 by https://github.com/theforeman/foreman/commit/a377f776e51d6b046ad0d28a56d1427777a51797