1. click the button above to set listitem invisible.
2. check select all checkbox.
3. observe the browser console. javascript errors occurred.

a workaround:
zk.afterLoad('zul.sel', function() {
function _isListgroup(w)

{ return zk.isLoaded('zkex.sel') && w.$instanceof(zkex.sel.Listgroup); }

function _isListfoot(w)

{ return w.$instanceof(zul.sel.Listfoot); }

function _isListgroupfoot(w)

{ return zk.isLoaded('zkex.sel') && w.$instanceof(zkex.sel.Listgroupfoot); }

zk.override(zul.sel.SelectWidget.prototype, '_isAllSelected', function(){
if (!this._selItems.length)
return false;
var isGroupSelect = this.groupSelect;
for (var it = this.getBodyWidgetIterator(

{skipHidden:true}

), w; (w = it.next())

{ if ((_isListgroup(w) || _isListgroupfoot(w) || _isListfoot(w)) && !isGroupSelect) continue; if (!w.isDisabled() && !w.isSelected()) return false; }

return true;
});
});