entity_browser_entity_form_field_widget_third_party_settings_form hooks can no longer return NULL

Merge request created.

This could probably use a test.

Could an additional assertion be added somewhere?

A test would require another hook that returns nothing. I'm not sure that's really worth it.

I'm also not sure we actually want to support this. we could also explicitly deprecate a non-array return value.

either way, leaving at needs work to update the second place

Updated the second place. I think it would be nice to get this in before 11.2 and avoid fatal errors. I can fix entity_browser but others might be affected too.

If we don't add tests could we add steps for manual testing to trigger this error?

Added STR, I don't remember 100% if it already happens when you visit the form display page or if you need to click the gear icon of a given field, but one or the other should reproduce the error.