fix many PHP 8.4 compatibility issues

libs/FML/Controls/Frame.php

@@ -103,7 +103,7 @@ class Frame extends Control implements Container
      * @deprecated Use Style
      * @see        Style
      */
-    public function setFormat(Format $format = null)
+    public function setFormat(?Format $format = null)
     {
         $this->format = $format;
         return $this;