Wt

Hi, I have a problem with my application, it destroys after certain actions with the following errors:

1712 [2022-Oct-06 15:51:18.046] 179168 [/ YSMN1DEmShN9BxQm] [error] "Wt: error during event handling: WContainerWidget: error parsing: undefined"                                       
1713 [2022-Oct-06 15:51:18.047] 179168 [/ YSMN1DEmShN9BxQm] [error] "Wt: fatal error: WContainerWidget: error parsing: undefined"

I use one WTabWidget inside of another and I use setOverflow(Wt::Overflow::Visible) for them.
wt_config.xml has the reload-is-new-session option set to false.

Steps to reproduce are:

1. Refresh page
2. Click on checkbox

After that session is destroyed. If I don't use setOverflow(Wt::Overflow::Visible), session is not destroyed and everything works as expected.
Tested on versions 4.7.3, 4.8.1

Here's minimal example:

  auto containerOuterTab = std::make_unique<WContainerWidget>();
  auto containerInnerTab = std::make_unique<WContainerWidget>();

  auto tabWidgetOuter = this             ->addNew<WTabWidget>();
  auto tabWidgetInner = containerOuterTab->addNew<WTabWidget>();

  containerInnerTab->addNew<WCheckBox>("Checkbox")->changed().connect([this]() { std::cout << "Checkbox changed" << std::endl; });

  tabWidgetOuter->setOverflow(Wt::Overflow::Visible);
  tabWidgetOuter->addTab(std::move(containerOuterTab), "Outer tab");

  tabWidgetInner->setOverflow(Wt::Overflow::Visible);
  tabWidgetInner->addTab(std::move(containerInnerTab), "Inner tab");