[BUGFIX] Correctly check TSFE->rootLine

The existing check on the data-type of $rootLine has to be adjusted
since the default value is now an array.

Resolves: #89512
Related: #89482
Releases: master, 9.5
Change-Id: Ia1d673ff2fe1f45e615c5bc6c81b574b63ec2e54
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/62112
Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Benni Mack <benni@typo3.org>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Benni Mack <benni@typo3.org>

typo3/sysext/frontend/Classes/Controller/TypoScriptFrontendController.php

@@ -1691,7 +1691,7 @@ public function getPageAndRootlineWithDomain($rootPageId)
     {
         $this->getPageAndRootline();
         // Checks if the $domain-startpage is in the rootLine. This is necessary so that references to page-id's from other domains are not possible.
-        if ($rootPageId && is_array($this->rootLine)) {
+        if ($rootPageId && is_array($this->rootLine) && $this->rootLine !== []) {
             $idFound = false;
             foreach ($this->rootLine as $key => $val) {
                 if ($val['uid'] == $rootPageId) {