[gnome-builder] flatpak: fix invalid cast from notification to widget

[Christian Hergert <chergert src gnome org>]

commit 589cb07a4013f984c3355b2ecce211d7fa0f166f
Author: Christian Hergert <chergert redhat com>
Date:   Fri Mar 6 10:22:06 2020 -0800

    flatpak: fix invalid cast from notification to widget
    
    This should be instead withdrawing the notification.

 src/plugins/flatpak/gbp-flatpak-workbench-addin.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
---
diff --git a/src/plugins/flatpak/gbp-flatpak-workbench-addin.c 
b/src/plugins/flatpak/gbp-flatpak-workbench-addin.c
index 0e3d473b8..8209cef33 100644
--- a/src/plugins/flatpak/gbp-flatpak-workbench-addin.c
+++ b/src/plugins/flatpak/gbp-flatpak-workbench-addin.c
@@ -195,7 +195,8 @@ gbp_flatpak_workbench_addin_install_cb (GObject      *object,
        *       because we know it is invalidated.
        */
       g_signal_emit_by_name (config_manager, "invalidate");
-      gtk_widget_hide (GTK_WIDGET (self->message));
+      ide_notification_withdraw (self->message);
+      g_clear_object (&self->message);
     }
 
   IDE_EXIT;