undefined method `reflect_on_association' for NilClass:Class

[arun057]

I am trying to do a 4 level deeply nested form, but plugin fails at the second level of nesting.
for example,

Course -> Lessons -> Sections -> Assets
plugin works for lessons when only that is using the link_to_add helper.

when I add it to Sections, and Assets it fails with

  undefined method `reflect_on_association' for NilClass:Class

at

  <%= render 'asset_fields', f: asset_builder %>
  <% end %>
  <br/>
  <%= f.link_to_add "Add Asset", :assets %>
  </fieldset>

[lest]

Could you please push a test application reproducing this issue? Thanks!

[arun057]

Looks like it was my fault, I had a belongs to , :through on my asset model (dunno why the dev server didnt throw any error though :( )