Ticket #33509: 33509.diff

wp-admin/js/customize-controls.js

@@ -1497 +1497 @@
                  * @param {Callback} args.completeCallback
                  */
                 onChangeActive: function ( active, args ) {
-                        if ( ! $.contains( document, this.container ) ) {
+                        if ( this.container[0] && ! $.contains( document, this.container[0] ) ) {
                                 // jQuery.fn.slideUp is not hiding an element if it is not in the DOM
                                 this.container.toggle( active );
                                 if ( args.completeCallback ) {