fix: list() and references can cause fatal errors, closes #3491

Author: thorsten

phpmyfaq/src/phpMyFAQ/Category/Order.php

@@ -127,7 +127,9 @@ public function getCategoryTree(array $categories, int $parentId = 0): array
         $stack = [[$parentId, &$result]];
 
         while (!empty($stack)) {
-            list($currentParentId, &$currentResult) = array_pop($stack);
+            $popped = array_pop($stack);
+            $currentParentId = $popped[0];
+            $currentResult = &$popped[1];
 
             foreach ($categories as $category) {
                 if ((int) $category['parent_id'] === $currentParentId) {