tabs destroy functionality broken

I saw this error before, but only since FF4 it's always there. So I took my time to investigate a bit

Here is how to reproduce this error.

Build a custom download over http://jqueryui.com/download

Modify the index.html demo page

from

//hover states on the static widgets
$('#dialog_link, ul#icons li').hover(
					function() { $(this).addClass('ui-state-hover'); }, 
					function() { $(this).removeClass('ui-state-hover'); }
				);

to

//hover states on the static widgets
$('#dialog_link, ul#icons li').hover(
					function() { $(this).addClass('ui-state-hover'); }, 
					function() { $(this).removeClass('ui-state-hover'); }
				);

				$(window).unload(function() {
					$('#tabs').tabs('destroy'); 
					}
				);

Reload the page in FF4 with Firebug Console open. Also keep old error messages on.

Error message appears

this.panels is null

in jquery.ui.tabs.js this is in the function abort() line 673

I have not much idea of the inner workings, but I noticed the lines

225 to 230 in jquery.ui.tabs.js which is indicated to be an IE6 hack and

amongst other things does a

self.panels = null in line 229

I removed self.panels from being set to null. The original error then disappeared, but I was getting another error this.lis is null which is in function _cleanup() line 91

At that point I abandoned hope to patch this issue myself. The quick fix would be to check for if (this.panels == null), etc. But that cures the symptoms and not the real issue which is that all the unload logic never gets run through properly.

Commenting out lines 229 does silence Firebug, but if that's the proper solution, and what IE6 does with it I don't know.