Add missing callback param to dw_toggle

lib/scripts/behaviour.js

-/*jslint sloppy: true */
-/*global jQuery, LANG, document, alert */
-
 /**
  * Automatic behaviours
  *
@@ -170,13 +167,13 @@ jQuery.fn.dw_show = function(fn) {
  *
  * @param bool the current state of the element (optional)
  */
-jQuery.fn.dw_toggle = function(bool) {
+jQuery.fn.dw_toggle = function(bool, fn) {
     return this.each(function() {
         var $this = jQuery(this);
         if (typeof bool === 'undefined') {
             bool = $this.is(':hidden');
         }
-        $this[bool ? "dw_show" : "dw_hide" ]();
+        $this[bool ? "dw_show" : "dw_hide" ](fn);
     });
 };