[BUGFIX] Ensure string return value in Uri\PageViewHelper

Force the return value to be a string if the uri to a page is generated
but the provided page is not existing or hidden and no child node is
provided.

Resolves: #99502
Releases: main, 11.5
Change-Id: Ia2300d107bed03d8cc26efdc13b48cb4fb3dbcc0
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/77312


Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Achim Fritz <af@achimfritz.de>
Tested-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Benni Mack <benni@typo3.org>
Tested-by: Achim Fritz <af@achimfritz.de>
Reviewed-by: Benni Mack <benni@typo3.org>
Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Tested-by: core-ci <typo3@b13.com>