[TASK] Sanitize idn_to_ascii with empty string

idn_to_ascii() must not be called with empty
string in PHP 8.4.

Resolves: #104587
Related: #104513
Releases: main, 12.4, 11.5
Change-Id: I649d157cca3dadbe237e20eb440b071a1885db71
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/85581


Reviewed-by: Stefan Bürk <stefan@buerk.tech>
Tested-by: core-ci <typo3@b13.com>
Tested-by: Stefan Bürk <stefan@buerk.tech>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Jasmina Ließmann <minapokhalo+typo3@gmail.com>
Tested-by: Jasmina Ließmann <minapokhalo+typo3@gmail.com>
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/85583

typo3/sysext/core/Classes/Routing/SiteMatcher.php

@@ -245,7 +245,7 @@ class SiteMatcher implements SingletonInterface
         $requestContext = new RequestContext(
             '',
             $request->getMethod(),
-            (string)idn_to_ascii($uri->getHost()),
+            $uri->getHost() ? (string)idn_to_ascii($uri->getHost()) : '',
             $uri->getScheme(),
             // Ports are only necessary for URL generation in Symfony which is not used by TYPO3
             80,