AttachScreenshot applet - when you cancel the dialog, you end up with empty screenshot-redirecter.jsp popup

Apparently recent changes to the jsp:

 var afterURL = document.getElementById("afterURL").firstChild.nodeValue;

cause NPE in Javascript (always when the applet is dismissed by "Cancel" button).

I know it's being fixed for 4.1.2 (due to other problems), but I did not see any bug report showing that this very problem.
So here it comes.