"Browse" dialogs are not modal when they should be

1. Go to "Tools" -> "Options..." -> "Kits" -> "Qt Versions".
2. Click the "Add..." button.
   A dialog will open.
3. Click on "Add..." again.
   Nothing happens.
4. Click on a different Tab of the Options dialog.
   Nothing happens.
5. In the dialog that showed up in step 2, click "Cancel" to close it.
   The dialog closes and reappears immediately, this time triggered by step 3.
6. In that dialog, click "Cancel" to close it.
   The Options dialog switches to the tab you clicked in step 4.

I can only reproduce this with Creator from the binary installer running on Linux.

The "Browse" dialog should be modal so you couldn't click anything in the Options dialog while it is open. This seems to be the case in my own builds as well as on Windows.