Add a link to edit a text shout

This link does not currently work.
The error message undefined method `model_name' for TextShout::ActiveRecord_Relation:Class
keeps appearing no matter how I approach the problem.

1) Methods used: edit_polymorphic_path(shout)
2) Exclude resources :content, nested under both text_shouts and photo_shouts
3) ActivModel::Naming

And some others.

@gabebw
Does `@text_shout = Shout.where(content_type: "TextShout", content_id: params[:id]).content`, with `form_for @text_shout`, not work?