[BUGFIX] Ensure string in htmlspecialchars()

When select fields with db relations allow pages
records, the DatabaseBrowser tries to render an
icon from the page row. uid of that row may be
an int, which needs to be cast to string to be
fed to htmlspecialchars().

Resolves: #101513
Related: #100819
Releases: main, 12.4, 11.5
Change-Id: I52ee031cb0eb09f41ae8ecb6d7005f03e65de3bd
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/80285


Tested-by: core-ci <typo3@b13.com>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>