Child item without zone has no details displayed

Refs https://redmine.teklia.com/issues/5487

When a child item on an element with a zone has itself no zone, the frontend prevents selecting it and displaying its detail.

I agree this is a weird case that has little sense data-wise (in the ref example, the household should be at the level above (folder) as it's supposed to represent multi-page elements). But the frontend should:

• display the info notification as currently 👍
• update the right side with element base informations