Incompatibility with attribute grouping (Administrate 0.20.0)

[CharlotteBory]

The latest version of Administrate groups attributes.
The return value for Field#attributes is now a Hash {"Group title" => [Field, Field]} rather than an Array [Field, Field]. This is incompatible with the current version, throwing Undefined method 'attributes' for "":String (NoMethodError) where "" is the group title.

This is where the error is first raised:

# lib/administrate/field/nested_has_many.rb

  def nested_fields
    associated_form.attributes.reject do |nested_field|
      skipped_fields.include?(nested_field.attribute)
    end
  end

I may be able to make a PR to handle the new format but in the meantime I wanted to document my findings.

[nickcharlton]

Oh, dammit! Thanks for noticing that and opening this.

If you could try with a PR, that'd be great! Let me know if you need any help.

[gustavosobral]

We just updated to administrate v0.20 and noticed the same issue. Looking forward for the #66 fix 🙇