Crash on emitting a signal from C++ to QML with undefined QJSValue

class Messenger : public QQuickItem
{
    Q_OBJECT
public:
    explicit Messenger(QQuickItem *parent = 0);

signals:
    void received(QJSValue message);

public slots:
    void send (QJSValue message = QJSValue());
};

void Messenger::send(QJSValue message)
{
    emit received(message);
}

    Messenger {
        id: messenger
        onReceived: {
            console.log("hello");
        }
    }

    Component.onCompleted: {
        messenger.send(); // crash here
    }

QML debugging is enabled. Only use this in a safe environment.
Error: signal 11:
0   qtbug                               0x000000010add87a2 _Z15handleBacktracei + 34
1   libsystem_platform.dylib            0x00007fffe45c2bba _sigtramp + 26
2   ???                                 0x000000011684e7ad 0x0 + 4672776109
3   QtQml                               0x000000010b33f39d _ZN15QQmlBoundSignal10setEnabledEb + 477
4   QtQml                               0x000000010b38106d _ZN12QQmlNotifier10emitNotifyEP20QQmlNotifierEndpointPPv + 781
5   QtCore                              0x000000010b850fc9 _ZN11QMetaObject8activateEP7QObjectiiPPv + 121
6   qtbug                               0x000000010addac4f _ZN9Messenger8receivedE8QJSValue + 63