AwesomeNestedSet + Rails 4.1.4 `nested_set_options` throws exception

I have a model called Collection that is configured as such:

acts_as_nested_set scope: :account, dependent: :destroy
belongs_to :parent, class_name: 'Collection'

Using the nested_set_options view helper worked fine until I upgraded to Rails 4.1.4 (up from 4.0.5):

<%= f.input :parent_id, label: 'Parent Collection',
            collection: nested_set_options(@collections) { |collection|
              "#{'-' * collection.level} #{collection.name}"
            },
            include_blank: '-- No Parent --' %>

I get this exception:

undefined method `name' for nil:NilClass

/Users/cpeters/Sites/plugins/awesome_nested_set/lib/awesome_nested_set/model.rb:45:in  `add_to_inverse_association'
/Users/cpeters/Sites/plugins/awesome_nested_set/lib/awesome_nested_set/model.rb:37:in `block in associate_parents'
activerecord (4.1.4) lib/active_record/relation/delegation.rb:46:in `each'
activerecord (4.1.4) lib/active_record/relation/delegation.rb:46:in `each'
/Users/cpeters/Sites/plugins/awesome_nested_set/lib/awesome_nested_set/model.rb:31:in `associate_parents'
/Users/cpeters/Sites/plugins/awesome_nested_set/lib/awesome_nested_set/helper.rb:33:in `block in nested_set_options'
/Users/cpeters/Sites/plugins/awesome_nested_set/lib/awesome_nested_set/helper.rb:32:in `each'
/Users/cpeters/Sites/plugins/awesome_nested_set/lib/awesome_nested_set/helper.rb:32:in `nested_set_options'
app/views/admin/resources/collections/_form.html.erb:7:in `block in _app_views_admin_resources_collections__form_html_erb__1427458998633439544_70350945783440'

This is running the latest from GitHub (commit f823ffb).

As it turns out, my belongs_to configuration was not needed and was causing the problem.

I removed this line from the model, and all of my tests are passing, and the app works fine:

belongs_to :parent, class_name: 'Collection'

Not sure if I put that in there for a reason earlier, but I feel that having even one line less of code is a victory.