[DOCS] Fix examples of AfterPageTreeItemsPreparedEvent

Resolves TYPO3-Documentation/Changelog-To-Doc#1175

Releases: main, 13.4, 12.4

Documentation/ApiOverview/Events/Events/Backend/AfterPageTreeItemsPreparedEvent.rst

@@ -21,6 +21,7 @@ class after the page tree items have been resolved and prepared. The event
 provides the current PSR-7 request object as well as the page tree items. All
 items contain the corresponding page record in the special :php:`_page` key.
 
+..  _AfterPageTreeItemsPreparedEvent-labels:
 
 Labels
 ======
@@ -37,6 +38,7 @@ A label can also be assigned to a node via
 only the marker for the label with the highest priority is rendered. All
 additional labels will only be added to the title of the node.
 
+..  _AfterPageTreeItemsPreparedEvent-status:
 
 Status information
 ==================
@@ -53,6 +55,7 @@ accessibility.
 Each node can accommodate multiple status information, prioritized by severity
 and urgency. Critical messages take precedence over other status notifications.
 
+..  _AfterPageTreeItemsPreparedEvent-example:
 
 Example
 =======
@@ -63,6 +66,8 @@ Example
 
 ..  include:: /_includes/EventsAttributeAdded.rst.txt
 
+..  _AfterPageTreeItemsPreparedEvent-api:
+
 API
 ===
 

Documentation/ApiOverview/Events/Events/Backend/_AfterPageTreeItemsPreparedEvent/_MyEventListener.php

@@ -19,7 +19,7 @@ public function __invoke(AfterPageTreeItemsPreparedEvent $event): void
     {
         $items = $event->getItems();
         foreach ($items as &$item) {
-            if ($item['_page']['uid'] === 123) {
+            if (($item['_page']['pid'] ?? null) === 123) {
                 // Set special icon for page with ID 123
                 $item['icon'] = 'my-special-icon';