Missing constructor params crashes program

When a QMetaObject is registered as a global object property, and a new instance of the class is created in the JS program, if the constructor in the JS program is missing parameters, the application will crash immediately.

In the following example, the Example class constructor takes a single parameter. When the constructor is called with no parameters from JS, the program will crash:

Example.h:

#include <QObject>

class Example : public QObject {
    Q_OBJECT
public:
    Q_INVOKABLE Example (int id) { }
}; 

Program:

#include <QCoreApplication>
#include <QJSEngine>
#include <QDebug>
#include "example.h"

int main (int argc, char *argv[]) {
    QCoreApplication a(argc, argv);

    QJSEngine engine;
    QJSValue meta = engine.newQMetaObject(&Example::staticMetaObject);
    engine.globalObject().setProperty("Example", meta);

    //QString program = "new Example(123);";   // works fine
    QString program = "new Example();";        // crashes program
    QJSValue result = engine.evaluate(program);

    qDebug() << result.toString();
    qDebug() << "finished";

    return a.exec();
} 

Expected results: `evaluate` should return a JS error indicating that a parameter was missing (or some default constructed value should be passed as the parameter, which would be more in line with JS behavior).

Actual results: The program will crash when `new Example()` is executed.

Note: The program runs fine if `new Example(123)` is executed instead.