macOS: FileDialog.open() hangs after setting a different folder from previous one

In QtQuick,

FIleDialog open() -> select folder "A" -> close() -> set folder "B" to fileDialog.folder -> open() will hang the application.

This happens on macOS10.15 but not on macOS 10.14.

How to reproduce.
1. Run the sample code (qtbug80525.zip)
2. Click "open dialog" button
3. Set some other folder than Desktop and close the dialog
4. Press "set Desktop" button
5. Click "open dialog"
-> Application hangs