XWiki terminal pages are not excluded on the page creation form

Reproduction steps

1. Open an XWiki backend
2. find a hierarchy with a page A.WebHome and A.B (the latter is terminal)
3. click on the new page button
4. Type a name C
5. Select A.B in the document tree
6. click on create
7. edit and save
8. observe the hierarchy

Expected

The terminal pages are excluded or disabled so that user are prevented from selecting them.

From a user point of view, unaware of the notion of terminal pages,  A.B.C is expected.
Actual

Actual

A.C is created instead of the expected A.B.C.