[gnome-applets/wip/muktupavels/werror] drivemount: fix -Wswitch-default warning

[Alberts Muktupāvels <muktupavels src gnome org>]

commit b90f9f4b93ad401352dbae604287a22eb19d7a22
Author: Alberts Muktupāvels <alberts muktupavels gmail com>
Date:   Sat Apr 4 22:03:31 2020 +0300

    drivemount: fix -Wswitch-default warning

 gnome-applets/drivemount/drive-button.c | 2 ++
 1 file changed, 2 insertions(+)
---
diff --git a/gnome-applets/drivemount/drive-button.c b/gnome-applets/drivemount/drive-button.c
index 0160affce..65d617b7a 100644
--- a/gnome-applets/drivemount/drive-button.c
+++ b/gnome-applets/drivemount/drive-button.c
@@ -236,6 +236,8 @@ drive_button_key_press (GtkWidget      *widget,
                            0, event->time);
        }
        return TRUE;
+    default:
+       break;
     }
     return FALSE;
 }