Index: branches/RC/core/admin_templates/tree.tpl
===================================================================
diff -u -N -r11749 -r11963
--- branches/RC/core/admin_templates/tree.tpl	(.../tree.tpl)	(revision 11749)
+++ branches/RC/core/admin_templates/tree.tpl	(.../tree.tpl)	(revision 11963)
@@ -12,7 +12,12 @@
 	}
 
 	function onTreeFrameResize() {
-		var $width = $('#sub_frameset', window.parent.document).attr('cols').split(',')[0];
+		var $frameset = $('#sub_frameset', window.parent.document);
+		if (!$frameset.length) {
+			return ;
+		}
+
+		var $width = $frameset.attr('cols').split(',')[0];
 		if (($width <= 0) || ($width == $last_width)) {
 			// don't save zero width
 			return ;