Summary: Guard adding a back slash to the directory name with an if (!= null) check
Reviewed-by: anthony, art
Contributed-by: NMatt <melkor@orangepalantir.org>

Reviewed-by: dcherepanov, dav, art, denis

Reviewed-by: dholmes

Reviewed-by: art, anthony

Summary: Override GtkFileDialogPeer.toFront()
Reviewed-by: art, dcherepanov

Reviewed-by: art, dcherepanov

Summary: Add the trailing slash if it's absent
Reviewed-by: art, dcherepanov

Reviewed-by: darcy, weijun

Summary: Introduce a GTK-based alternative implementation of the FileDialogPeer on X11
Reviewed-by: anthony, peterz
Contributed-by: NCostantino Cerbo <c.cerbo@gmail.com>