[gnome-control-center] user-accounts: Fix user carousel not showing

[Georges Basile Stavracas Neto <gbsneto src gnome org>]

commit 71eefdd8f6d5013bf703cf8e6ea46cb84caaad3e
Author: Robert Ancell <robert ancell canonical com>
Date:   Wed Oct 24 10:56:40 2018 +1300

    user-accounts: Fix user carousel not showing
    
    This bug was introduced in 02559b0f697f1e87132adf68f01e81bda0696544

 panels/user-accounts/um-carousel.c | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/panels/user-accounts/um-carousel.c b/panels/user-accounts/um-carousel.c
index 167196a96..7616a9a98 100644
--- a/panels/user-accounts/um-carousel.c
+++ b/panels/user-accounts/um-carousel.c
@@ -310,6 +310,7 @@ um_carousel_add (GtkContainer *container,
                 gtk_stack_add_named (self->stack, self->last_box, page);
         }
 
+        gtk_widget_show_all (widget);
         gtk_box_pack_start (GTK_BOX (self->last_box), widget, TRUE, FALSE, 10);
 
         update_buttons_visibility (self);