PHP 8.4 fix for null param

Info:
https://dev.to/gromnan/fix-php-84-deprecation-implicitly-marking-parameter-as-nullable-is-deprecated-the-explicit-nullable-type-must-be-used-instead-5gp3

class.krumo.php

@@ -677,7 +677,7 @@ public static function setLineNumberTestCallback($callback)
      *
      * @param array $cascade Cascading information
      */
-    public static function cascade(array $cascade = null)
+    public static function cascade(?array $cascade = null)
     {
         static::$_cascade = $cascade;
     }