[BUGFIX] Avoid 500 error for non-admins in page tree

This patch prevents throwing and spamming the logs
with 500 server errors.

Resolves: #91145
Releases: master, 9.5
Change-Id: I9385a9c0a2a665cedb1340cc8397740b0bd6255e
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/64150
Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Andreas Fernandez <a.fernandez@scripting-base.de>

typo3/sysext/backend/Classes/Controller/Page/TreeController.php

@@ -247,6 +247,9 @@ protected function pagesToFlatArray(array $page, int $entryPoint, int $depth = 0
         if (in_array($pageId, $this->hiddenRecords, true)) {
             return [];
         }
+        if ($pageId === 0 && !$backendUser->isAdmin()) {
+            return [];
+        }
 
         $stopPageTree = !empty($page['php_tree_stop']) && $depth > 0;
         $identifier = $entryPoint . '_' . $pageId;