Exception when adding a variant for a product with no master price

[ok32]

Solidus Version: 3.2.5

To Reproduce

1. create a product
2. delete the master price in the default currency (config.currency)
3. attempt creating a new variant
4. see the exception: undefined method 'attributes' for nil:NilClass pointing to https://github.com/solidusio/solidus/blob/739b2a63cc3079b8256f8b85816a5a3d81689b76/backend/app/controllers/spree/admin/variants_controller.rb#L19

Current behavior

There's an exception.

Expected behavior

A more friendly behavior is expected.

Screenshots