Steps to Reproduce

1. open the listheader popup > group
2. change to page 3
3. collapse "Group 002"

Current Result

java.lang.ClassCastException: class org.zkoss.zul.Listitem cannot be cast to class org.zkoss.zul.Listgroup (org.zkoss.zul.Listitem and org.zkoss.zul.Listgroup are in unnamed module of loader 'app')
at org.zkoss.zul.impl.ListboxDataLoader.doGroupsDataChange(ListboxDataLoader.java:104)
at org.zkoss.zul.Listbox.onGroupsDataChange(Listbox.java:2668)
at org.zkoss.zul.Listbox.access$1100(Listbox.java:283)
at org.zkoss.zul.Listbox$5.onChange(Listbox.java:505)
at org.zkoss.zul.AbstractGroupsModel.fireEvent(AbstractGroupsModel.java:72)
at org.zkoss.zul.GroupsModelArray.setOpenGroup0(GroupsModelArray.java:254)
at org.zkoss.zul.GroupsModelArray.removeOpenGroup(GroupsModelArray.java:240)
at org.zkoss.zul.Listgroup.service(Listgroup.java:220)
at org.zkoss.zk.ui.impl.DesktopImpl.service(DesktopImpl.java:793)
at org.zkoss.zk.ui.impl.UiEngineImpl.execUpdate(UiEngineImpl.java:1312)
at org.zkoss.zk.au.http.DHtmlUpdateServlet.process(DHtmlUpdateServlet.java:571)
at org.zkoss.zk.au.http.DHtmlUpdateServlet.doGet(DHtmlUpdateServlet.java:451)
at org.zkoss.zk.au.http.DHtmlUpdateServlet.doPost(DHtmlUpdateServlet.java:459)

Expected Result

no error