90° X rotation as quaternion produces NaN on euler angle

A node with rotation set to Qt.quaternion(0.707107,0.707107,0,0) will give an eulerRotation of QVector3D(nan, 0, 0).

The problem occurs with +/-0.707107 on X axis but not on Y or Z axis.

Any other value did not produce error

How to reproduce :

    Model {
        rotation: Qt.quaternion(0.707107,0.707107,0,0)
        Component.onCompleted: {
            console.log(rotation + "\t" + eulerRotation)
        }
    }

UPDATE :

The issue is not with QML but with QQuaternion class. We can test it with

    QQuaternion q = QQuaternion(0.707107,-0.707107,0,0);
    std::cout << q.toEulerAngles().x() << "\n";