FileDialog using selectFolder freezes when there are unavailable network volumes

I am developing a QML application that uses `FileDialog` component to select folders using the `selectFolder` property.

On Windows, when there are unavailable network drives (volumes that exist but are not on the current network), the application freezes for at least 10 seconds when a `FileDialog` is instantiated.

See the attached example code to reproduce the issue:

1. Connect to a network drive on Network A
2. Start the example
3. Switch over to another network so that the drive is no longer accessible (e.g. 4G connection or whatever)
4. Click on the "click me" button
5. Witness the freeze

The application only freezes the first time the "Click me" button is clicked after the network drive is no longer accessible. The only way to have the freeze again is to make the network drive available then not available again, then re-clicking on the "Click me" button.

P.S. Using FolderDialog from Qt.labs.platform does not work for me because of a difference in behavior between the QtQuick.Dialogs and Qt.labs.platform implementation.