[gnome-mahjongg/arnaudb/wip/gtk4: 15/29] Adapt to MenuButton API.

[Arnaud B. <arnaudb src gnome org>]

commit 1694de469c7b26169ea0a3d8a6fc1ec99d8c3b7d
Author: Arnaud Bonatti <arnaud bonatti gmail com>
Date:   Fri Mar 27 19:06:55 2020 +0100

    Adapt to MenuButton API.

 src/gnome-mahjongg.vala | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/src/gnome-mahjongg.vala b/src/gnome-mahjongg.vala
index c9b6700..b3d0e61 100644
--- a/src/gnome-mahjongg.vala
+++ b/src/gnome-mahjongg.vala
@@ -163,7 +163,7 @@ public class Mahjongg : Gtk.Application
         menu_button = new Gtk.MenuButton ();
         menu_button.valign = Gtk.Align.CENTER;
         menu_button.set_menu_model (menu);
-        menu_button.set_image (new Gtk.Image.from_icon_name ("open-menu-symbolic", Gtk.IconSize.BUTTON));
+        menu_button.set_icon_name ("open-menu-symbolic");
 
         var header_bar = new Gtk.HeaderBar ();
         header_bar.set_custom_title (title_box);