[gtk/matthiasc/for-master] gtk-demo: Fix a problem with the dnd demo

[Matthias Clasen <matthiasc src gnome org>]

commit 7eaa10dd8edd0534b6a92fd3ef7c8b6a306b5029
Author: Matthias Clasen <mclasen redhat com>
Date:   Thu May 14 01:16:56 2020 -0400

    gtk-demo: Fix a problem with the dnd demo
    
    When I move this into gtk-demo, I broke the hack
    that ensures the GtkColorSwatch type is registered.
    Bring it back.

 demos/gtk-demo/dnd.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)
---
diff --git a/demos/gtk-demo/dnd.c b/demos/gtk-demo/dnd.c
index a3445e774f..6583d82f60 100644
--- a/demos/gtk-demo/dnd.c
+++ b/demos/gtk-demo/dnd.c
@@ -419,6 +419,7 @@ do_dnd (GtkWidget *do_widget)
 {
   if (!window)
     {
+      GtkWidget *button;
       GtkWidget *sw;
       GtkWidget *canvas;
       GtkWidget *box, *box2, *box3;
@@ -431,7 +432,8 @@ do_dnd (GtkWidget *do_widget)
       int i;
       int x, y;
 
-      g_type_ensure (GTK_TYPE_COLOR_BUTTON);
+      button = gtk_color_button_new ();
+      g_object_unref (g_object_ref_sink (button));
 
       window = gtk_window_new ();
       gtk_window_set_display (GTK_WINDOW (window),