QMediaDevices::videoInputs returns empty list when used alone

#include <QCoreApplication>
#include <QtCore>
#include <QCameraDevice>
#include <QMediaDevices>
#include <QAudioDevice>

int main(int argc, char *argv[])
{
    init_messages_name();    QCoreApplication app(argc, argv);
    // If this is left out, videoInputDevices.count() is zero, otherwise 1 and returns the correct webcam.
    const auto audioInputs = QMediaDevices::audioInputs();
    const auto videoInputDevices = QMediaDevices::videoInputs();
    qDebug() << videoInputDevices.count();    
    return app.exec();
}