When a hostgroup facet has been registered, along with a host facet and inheritable attributes, then any attempts to select a hostgroup that has no instance of said hostgroup facet errors out with a NoMethodError.

The stacktrace in question;

  from app/models/concerns/facets/hostgroup_extensions.rb:25:in `inherited_facet_attributes'
  from app/models/concerns/facets/base.rb:45:in `inherited_attributes'
  from app/models/concerns/facets/base_host_extensions.rb:18:in `block in apply_facet_attributes'
  from app/models/concerns/facets/base_host_extensions.rb:16:in `map'
  from app/models/concerns/facets/base_host_extensions.rb:16:in `apply_facet_attributes'
  from app/models/host/managed.rb:557:in `apply_inherited_attributes'
  from app/models/host/managed.rb:70:in `initialize'
  from active_record/inheritance.rb:66:in `new'
  from active_record/inheritance.rb:66:in `new'
  from app/models/concerns/foreman/sti.rb:19:in `new'
  from app/models/host.rb:15:in `method_missing'
  from app/controllers/hosts_controller.rb:661:in `refresh_host'
  from app/controllers/hosts_controller.rb:586:in `process_hostgroup'
  from action_controller/metal/basic_implicit_render.rb:6:in `send_action'

I looked through the call trace and it seems like there's nothing that actually checks if the hostgroup has an instance of the facet before attempting to read inherited attributes from it.