Ckfinder js error combination with ckeditor and onbeforeun..

Hello,

We are using ckeditor and ckfinder within an iframe in our CMS.
Before a user leaves the page if he has unsaved changes we do an onbeforeunload with the question if the user wants to stop leaving so he can save the page first.

We have the following problem:

If a user starts editing in CKEditor and opens CKFinder in a popup for browsing an image for example. It breaks the onbeforeunload in firefox. The error that is being thrown is: attempt to run compile-and-go script on a cleared scope on line: 3049 in the ckfinder.js (I have used http://jsbeautifier.org/ on ckfinder.js).

The same error also triggers in the demo however it doesn't show since the demo page doesn't use onbeforeunload.

Now I know that you can check if a window is closed so that you don't have to run script on a cleared scope.
I had contact with cksource about this error but their response is: "It seems that this is Firefox (v4 and above) bug which may get fixed eventually.".

Now I am wondering if anyone else had this same issue and maybe has a workaround for it?

Thanks in advance,

Jeffrey