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
No, I get the error: `First argument in form cannot contain nil or be empty`