[gnome-panel] force-quit: fix -Wswitch-default warning

[Alberts Muktupāvels <muktupavels src gnome org>]

commit 52246fc298ff963f879a372098074fc8ef65227f
Author: Alberts Muktupāvels <alberts muktupavels gmail com>
Date:   Sun Mar 8 01:21:07 2020 +0200

    force-quit: fix -Wswitch-default warning

 gnome-panel/panel-force-quit.c | 2 ++
 1 file changed, 2 insertions(+)
---
diff --git a/gnome-panel/panel-force-quit.c b/gnome-panel/panel-force-quit.c
index 73987c800..b6969a7c9 100644
--- a/gnome-panel/panel-force-quit.c
+++ b/gnome-panel/panel-force-quit.c
@@ -289,6 +289,8 @@ popup_filter (GdkXEvent *gdk_xevent,
                case XI_ButtonPress:
                        handle_button_press_event (popup, xidev->display, xidev->child);
                        return GDK_FILTER_REMOVE;
+               default:
+                       break;
                }
                break;
        default: