Simple use-case: categories and products
When editing the product an expanded (multiple) choice field of categories is displayed.
However when you create a product before you have created any category, there is simply the label/legend of the choice and some empty containers.

There are multiple solutions i came up with:

• Add a (configurable) "no choices available" message (my preferred solution)
• Just output nothing for form_row and form_widget; form_label behaves normal