[BUGFIX] Fix notice in FrontendConfigurationManager

Resolves: #99213
Releases: 11.5
Change-Id: I1a664d2e4b9c84063383769f956609390e8c3021
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/77371


Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Nikita Hovratov <nikita.h@live.de>
Tested-by: core-ci <typo3@b13.com>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Nikita Hovratov <nikita.h@live.de>

typo3/sysext/extbase/Classes/Configuration/FrontendConfigurationManager.php

@@ -126,7 +126,7 @@ class FrontendConfigurationManager extends AbstractConfigurationManager
         $pages = $this->contentObject->data['pages'] ?? '';
         if (is_string($pages) && $pages !== '') {
             $list = [];
-            if ($this->contentObject->data['recursive'] > 0) {
+            if ((int)($this->contentObject->data['recursive'] ?? 0) > 0) {
                 $explodedPages = GeneralUtility::trimExplode(',', $pages);
                 foreach ($explodedPages as $pid) {
                     $pids = $this->contentObject->getTreeList($pid, $this->contentObject->data['recursive']);