QFileDialog::getSaveFileName does not show native file picker in WinRT

Calling "QFileDialog::getSaveFileName" opens the Qt file picker instead of the the native Windows RT file picker for saving files. The open picker works fine.

The code for the file save picker is implemented in "qwinrtfiledialoghelper.cpp" but seems to fail to run.

The following errors are reported (although the file associations are defined in the manifest):

• Failed to set default file extension (Falscher Parameter.)
• Failed to insert file extension choice entry (Falscher Parameter.)

The dialog is called this way:

QFileDialog::getSaveFileName(0, tr("Export audio"), "", tr("wav (*.wav)"));