QToolButton::setMenu WebAssembly support (nested event loop)

I added a QToolButton to my form and in code called setMenu:

  auto filterMenu = new QMenu(ui->filterButton);
  ui->filterButton->setMenu(filterMenu);
  
  // Add actions to menu
  ...

Then I compiled it for webassembly, opened the browser and clicked on the tool button. The menu opens but the browser prints to console an ugly error message:

Seems the QToolButton menu internally calls exec() but Qt for WebAssembly does not support nested event loops.