[gnome-initial-setup/gnome-3-16] password: Avoid a critical

[Matthias Clasen <matthiasc src gnome org>]

commit 8862b619ff861db7acbc7e1f0990a0ca9e53c324
Author: Matthias Clasen <mclasen redhat com>
Date:   Wed Jul 8 14:40:35 2015 -0400

    password: Avoid a critical

 .../pages/password/gis-password-page.c             |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/gnome-initial-setup/pages/password/gis-password-page.c 
b/gnome-initial-setup/pages/password/gis-password-page.c
index fd557d7..25cd371 100644
--- a/gnome-initial-setup/pages/password/gis-password-page.c
+++ b/gnome-initial-setup/pages/password/gis-password-page.c
@@ -243,6 +243,7 @@ gis_password_page_constructed (GObject *object)
 static void
 gis_password_page_dispose (GObject *object)
 {
+  if (GIS_PAGE (object)->driver)
   g_signal_handlers_disconnect_by_func (GIS_PAGE (object)->driver,
                                         username_changed, object);