Empty String in JS is Converted to null QString in C++

class MyClass: QObject {
Q_OBJECT
public:
Q_INVOKABLE void testEmpty(QString s) {
    Q_ASSERT(!s.isNull());
}
Q_INVOKABLE void testUndefined(QString s) {
    Q_ASSERT(is.isNull());
}

};

In JS:

var obj = new MyClass();
obj.testEmpty("");
obj.testUndefined(undefined);

Expected:

• "" is converted to an empty, but non-null QString object
• undefined is converted to empty AND null QString object

Observed:

• QString is null in both cases

The QString documentation says explicitly:

QString().isNull();             // returns true
QString("").isNull();           // returns false
QString("abc").isNull();        // returns false

Therefore the current conversion behavior is not intuitive.