Fix issue where menu items with nesting=true wouldn't resolve their own URL

This fixes an issue introduced in 2d73dd2 where if the item had the nesting property set to true it would remove all previous data resolved about the individual item.

This had the effect of replacing the menu item's  URL with the URL for the first child under that menu item.

Author: LukeTowers

classes/Page.php

@@ -806,9 +806,9 @@ public static function resolveMenuItem(object $item, string $url, Theme $theme):
         }
 
         if ($item->nesting || $item->type == 'all-static-pages') {
-            $result = [
+            $result = array_merge($result ?? [], [
                 'items' => [],
-            ];
+            ]);
 
             $iterator = function ($items) use (&$iterator, &$tree, $url, $getLocalizedUrls) {
                 $branch = [];