[network-manager-pptp] service: fix critical errors in dispose()

[Jiří Klimeš <jklimes src gnome org>]

commit 5194e76cfada58c692df3911f8707204f06051ff
Author: Jiří Klimeš <jklimes redhat com>
Date:   Fri Nov 27 10:00:57 2015 +0100

    service: fix critical errors in dispose()
    
    It may happen when a gateway was wrong and thus dbus_skeleton was not initialized.
    
    (nm-pptp-service:8511): GLib-GObject-WARNING **: invalid (NULL) pointer instance
    (nm-pptp-service:8511): GLib-GObject-CRITICAL **: g_signal_handlers_disconnect_matched: assertion 
'G_TYPE_CHECK_INSTANCE (instance)' failed
    (nm-pptp-service:8511): GLib-GObject-WARNING **: invalid (NULL) pointer instance
    (nm-pptp-service:8511): GLib-GObject-CRITICAL **: g_signal_handlers_disconnect_matched: assertion 
'G_TYPE_CHECK_INSTANCE (instance)' failed
    (nm-pptp-service:8511): GLib-GObject-WARNING **: invalid (NULL) pointer instance
    (nm-pptp-service:8511): GLib-GObject-CRITICAL **: g_signal_handlers_disconnect_matched: assertion 
'G_TYPE_CHECK_INSTANCE (instance)' failed

 src/nm-pptp-service.c |    8 +++++---
 1 files changed, 5 insertions(+), 3 deletions(-)
---
diff --git a/src/nm-pptp-service.c b/src/nm-pptp-service.c
index 8b0eeb6..d56c56f 100644
--- a/src/nm-pptp-service.c
+++ b/src/nm-pptp-service.c
@@ -376,9 +376,11 @@ nm_pptp_ppp_service_dispose (GObject *object)
 {
        NMPptpPppServicePrivate *priv = NM_PPTP_PPP_SERVICE_GET_PRIVATE (object);
 
-       g_signal_handlers_disconnect_by_func (priv->dbus_skeleton, handle_need_secrets, object);
-       g_signal_handlers_disconnect_by_func (priv->dbus_skeleton, handle_set_state, object);
-       g_signal_handlers_disconnect_by_func (priv->dbus_skeleton, handle_set_ip4_config, object);
+       if (priv->dbus_skeleton) {
+               g_signal_handlers_disconnect_by_func (priv->dbus_skeleton, handle_need_secrets, object);
+               g_signal_handlers_disconnect_by_func (priv->dbus_skeleton, handle_set_state, object);
+               g_signal_handlers_disconnect_by_func (priv->dbus_skeleton, handle_set_ip4_config, object);
+       }
 
        G_OBJECT_CLASS (nm_pptp_ppp_service_parent_class)->dispose (object);
 }