[BUGFIX] Prevent PHP warnings in PageRouter

In some situations, "_page" might not be set
in the Route. This patch prevents undefined
array key warnings and also makes the code
more readable.

Resolves: #97369
Releases: main, 11.5
Change-Id: I47920cdeb641b52577590d710d692a91fca7c383
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/74284
Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Reviewed-by: Stefan Bürk <stefan@buerk.tech>
Reviewed-by: Nikita Hovratov <nikita.h@live.de>
Reviewed-by: Benni Mack <benni@typo3.org>
Reviewed-by: Oliver Bartsch <bo@cedev.de>
Tested-by: core-ci <typo3@b13.com>
Tested-by: Stefan Bürk <stefan@buerk.tech>
Tested-by: Nikita Hovratov <nikita.h@live.de>
Tested-by: Benni Mack <benni@typo3.org>
Tested-by: Oliver Bartsch <bo@cedev.de>

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

@@ -529,8 +529,13 @@ protected function buildPageArguments(Route $route, array $results, array $remai
             return $enhancer->buildResult($route, $results, $remainingQueryParameters);
         }
         $page = $route->getOption('_page');
-        $pageId = (int)(isset($page['t3ver_oid']) && $page['t3ver_oid'] > 0 ? $page['t3ver_oid'] : $page['uid']);
-        $pageId = (int)($page['l10n_parent'] > 0 ? $page['l10n_parent'] : $pageId);
+        if ((int)($page['l10n_parent'] ?? 0) > 0) {
+            $pageId = (int)$page['l10n_parent'];
+        } elseif ((int)($page['t3ver_oid'] ?? 0) > 0) {
+            $pageId = (int)$page['t3ver_oid'];
+        } else {
+            $pageId = (int)($page['uid'] ?? 0);
+        }
         $type = $this->resolveType($route, $remainingQueryParameters);
         // See PageSlugCandidateProvider where this is added.
         if ($page['MPvar'] ?? '') {