[REG 5.15.2->5.15.3]: ScxmlStateMachine submitEvent should not always expect data

My test code:

import QtScxml 5.8 as Scxml

Scxml.StateMachineLoader {
    id: myLoader
    source: "statemachine/App.scxml"
}

property QtObject stateApp: myLoader.stateMachine

stateApp.submitEvent("tr_goToEmergency") // Error insufficient arguments

In 5.15.3 I get the error at the last line: "Insufficient arguements"
The documentation says it should be possible: https://doc.qt.io/qt-5/qml-qtscxml-scxmlstatemachine.html#submitEvent-method-1

And it always worked okay up to Qt 5.15.2. It works when I add null as second argument, however this shouldn't be needed.