[Gtk-sharp-list] Unselecting file in FileChooserButton

[Thorsten Schoel]

To answer my own question:

I had to use a custom dialog and add a button with Dialog.AddButton with
ResponseType.Accept (to avoid the FileChooserButton to reset the file
name). In the Clicked event of this button I UnselectAll in the dialog.
Should have been obvious from the start, looking at my initial question.
Sorry for the spam.

Thorsten