Steps to Reproduce

Calling removeChildren on a server component which contains an iframe element in any depth.

Current Result

The server component is removed but the browser throws undefined exceptions in zul.wnd.Window.src.js "unbind"-function. 

Expected Result

Child widgets should be removed as well as server components

Debug Information

Maybe it has something todo with the added code:

#zul.wnd.Window.src.js
detach: function detach() {
// ZK-3910: the side effect of the removing iframe, the ckeditor would throw the error message
// at console. It should unbind ckeditor before remove it. Put here can works well on every browser.
      this.unbindChildren_(); // ZK-2247: remove iframe to prevent load twice

Workaround

We catch the exceptions and it seems to work.