QML signals don't send data when debugging and local variable is defined in the slot of another Component.

// Sending main.qml
Window {
    id: mainWindow

    signal test(var data)

    visible: true
    width: 640
    height: 480
    title: qsTr("Hello World")
    Timer {
        id: mytimer
        interval: 1000; running: true; repeat: true
        onTriggered: test("knock knock")
    }
    Component.onCompleted: {
        mytimer.start()
    }

    TestComponent { }

    onTest: {
        var localVar
        console.debug(data)
    }
}

// Receiving TestComponent.qml
Item {
    Connections {
        target: mainWindow
        onTest: {
            var test // comment this out and it works (also modify the source of the signal to update cache), why though?
            console.debug("test component: %1".arg(data)) // data is undefined!
        }
    }
}