[gtk+] demo: only set transient if demo returns a toplevel

[William Jon McCann <mccann src gnome org>]

commit 7ba0083fc9423619f160a13dc181d5776f55df7d
Author: William Jon McCann <william jon mccann gmail com>
Date:   Mon Dec 9 09:55:08 2013 +0100

    demo: only set transient if demo returns a toplevel

 demos/gtk-demo/main.c |    7 +++++--
 1 files changed, 5 insertions(+), 2 deletions(-)
---
diff --git a/demos/gtk-demo/main.c b/demos/gtk-demo/main.c
index 9de99cd..4e239d5 100644
--- a/demos/gtk-demo/main.c
+++ b/demos/gtk-demo/main.c
@@ -142,8 +142,11 @@ activate_run (GSimpleAction *action,
           cbdata->model = model;
           cbdata->path = gtk_tree_model_get_path (model, &iter);
 
-          gtk_window_set_transient_for (GTK_WINDOW (demo), GTK_WINDOW (window));
-          gtk_window_set_modal (GTK_WINDOW (demo), TRUE);
+          if (gtk_widget_is_toplevel (demo))
+            {
+              gtk_window_set_transient_for (GTK_WINDOW (demo), GTK_WINDOW (window));
+              gtk_window_set_modal (GTK_WINDOW (demo), TRUE);
+            }
 
           g_signal_connect (demo, "destroy",
                             G_CALLBACK (window_closed_cb), cbdata);