[gtk+] aboutdialog: Use set_boxed on surface

[Alexander Larsson <alexl src gnome org>]

commit 7a0ce9804f075ddf188d5dce703861c486f40e8a
Author: Alexander Larsson <alexl redhat com>
Date:   Mon Oct 23 12:48:11 2017 +0200

    aboutdialog: Use set_boxed on surface
    
    cairo_surface_t is boxed, not a GObject.

 gtk/gtkaboutdialog.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/gtk/gtkaboutdialog.c b/gtk/gtkaboutdialog.c
index 2fd7968..1534c5b 100644
--- a/gtk/gtkaboutdialog.c
+++ b/gtk/gtkaboutdialog.c
@@ -989,9 +989,9 @@ gtk_about_dialog_get_property (GObject    *object,
       break;
     case PROP_LOGO:
       if (gtk_image_get_storage_type (GTK_IMAGE (priv->logo_image)) == GTK_IMAGE_SURFACE)
-        g_value_set_object (value, gtk_image_get_surface (GTK_IMAGE (priv->logo_image)));
+        g_value_set_boxed (value, gtk_image_get_surface (GTK_IMAGE (priv->logo_image)));
       else
-        g_value_set_object (value, NULL);
+        g_value_set_boxed (value, NULL);
       break;
     case PROP_LOGO_ICON_NAME:
       if (gtk_image_get_storage_type (GTK_IMAGE (priv->logo_image)) == GTK_IMAGE_ICON_NAME)