Program: 20533
Project: 20533
Buggy source:
public EventListPanel(final UserModel userModel,final IModel<List<Event>> listModel){
  WebMarkupContainer listContainer=new WebMarkupContainer("String_Node_Str");
  add(listContainer);
  listContainer.add(new WebMarkupContainer("String_Node_Str"){
    @Override public boolean isVisible(){
      return listModel.getObject().isEmpty();
    }
  }
);
  listContainer.add(new EntityListView<Event>("String_Node_Str",listModel){
    @Override public boolean isVisible(){
      return !getList().isEmpty();
    }
    @Override protected void populateItem(    final ListItem<Event> item){
      final Event event=item.getModelObject();
      final EventModel eventModel=new EventModel(item.getModel());
      if (isNextEvent(event,getList())) {
        item.add(AttributeModifier.append("String_Node_Str","String_Node_Str"));
      }
      Link link=Links.eventLink("String_Node_Str",event.getId());
      item.add(link);
      link.add(new Label("String_Node_Str",Dates.formatDateShortWithWeekday(event.getDate())));
      link.add(new Label("String_Node_Str",Dates.formatTimeShort(event.getTime())));
      item.add(new Label("String_Node_Str",new ResourceModel(EventType.from(event).getResourceKey())));
      item.add(new Label("String_Node_Str",event.getTeam().getName()));
      item.add(new Label("String_Node_Str",event.getSummary()));
      final Invitation invitation=getInvitation(event,userModel.getObject());
      RSVPStatus status=invitation.getStatus();
      item.add(new QuickResponseLabel("String_Node_Str",status == RSVPStatus.NORESPONSE ? null : status){
        @Override protected void submitStatus(        final RSVPStatus status){
          responseManager.respond(eventModel.getId(),userModel.getId(),status);
        }
        @Override public boolean isEnabled(){
          return !eventManager.isEventClosed(event);
        }
      }
);
    }
    private Invitation getInvitation(    final Event event,    final User user){
      return invitationManager.loadByEventAndUser(event,user);
    }
  }
);
  listContainer.add(new AjaxEventListener(Event.class));
}

Fixed version (ground truth):
public EventListPanel(final UserModel userModel,final IModel<List<Event>> listModel){
  WebMarkupContainer listContainer=new WebMarkupContainer("String_Node_Str");
  add(listContainer);
  listContainer.add(new WebMarkupContainer("String_Node_Str"){
    @Override public boolean isVisible(){
      return listModel.getObject().isEmpty();
    }
  }
);
  listContainer.add(new EntityListView<Event>("String_Node_Str",listModel){
    @Override public boolean isVisible(){
      return !getList().isEmpty();
    }
    @Override protected void populateItem(    final ListItem<Event> item){
      final Event event=item.getModelObject();
      final EventModel eventModel=new EventModel(item.getModel());
      if (isNextEvent(event,getList())) {
        item.add(AttributeModifier.append("String_Node_Str","String_Node_Str"));
      }
      Link link=Links.eventLink("String_Node_Str",event.getId());
      item.add(link);
      link.add(new Label("String_Node_Str",Dates.formatDateShortWithWeekday(event.getDate())));
      link.add(new Label("String_Node_Str",Dates.formatTimeShort(event.getTime())));
      item.add(new Label("String_Node_Str",new ResourceModel(EventType.from(event).getResourceKey())));
      item.add(new Label("String_Node_Str",event.getTeam().getName()));
      item.add(new Label("String_Node_Str",event.getSummary()));
      final Invitation invitation=getInvitation(event,userModel.getObject());
      RSVPStatus status=invitation.getStatus();
      item.add(new QuickResponseLabel("String_Node_Str",status == RSVPStatus.NORESPONSE ? null : status){
        @Override protected void submitStatus(        final RSVPStatus status){
          responseManager.respond(eventModel.getId(),userModel.getId(),status);
        }
        @Override public boolean isEnabled(){
          return !eventManager.isEventClosed(item.getModelObject());
        }
      }
);
    }
    private Invitation getInvitation(    final Event event,    final User user){
      return invitationManager.loadByEventAndUser(event,user);
    }
  }
);
  listContainer.add(new AjaxEventListener(Event.class));
}