[libdazzle] app-window: use dzl_clear_signal_handler()

[Christian Hergert <chergert src gnome org>]

commit 3b5ce3a03b2b6172bf7af766ab6ce56575664c8b
Author: Christian Hergert <chergert redhat com>
Date:   Tue Sep 25 15:44:38 2018 -0700

    app-window: use dzl_clear_signal_handler()

 src/app/dzl-application-window.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)
---
diff --git a/src/app/dzl-application-window.c b/src/app/dzl-application-window.c
index 84a0aad..b435943 100644
--- a/src/app/dzl-application-window.c
+++ b/src/app/dzl-application-window.c
@@ -364,10 +364,7 @@ dzl_application_window_destroy (GtkWidget *widget)
   g_assert (DZL_IS_APPLICATION_WINDOW (self));
 
   if (priv->event_box != NULL)
-    {
-      g_signal_handler_disconnect (priv->event_box, priv->motion_notify_handler);
-      priv->motion_notify_handler = 0;
-    }
+    dzl_clear_signal_handler (priv->event_box, &priv->motion_notify_handler);
 
   g_clear_pointer ((GtkWidget **)&priv->titlebar_container, gtk_widget_destroy);
   g_clear_pointer ((GtkWidget **)&priv->titlebar_revealer, gtk_widget_destroy);