The crasher is caused by handling the signal "PositionProviderChanged" received
when the original GeoclueMasterClient connected to the
"PositionProviderChanged" signal is already disposed.

In geoclue-0.12.0_git0825\geoclue\geoclue-master-client.c, the implementation
of the constructor() connects the signal PositionProviderChanged with the
GeoclueMasterClientPrivate's proxy, but the signal is never disconnected when
the GeoclueMasterClientPrivate is destroyed in either finalize() or dispose().

When the signal "PositionProviderChanged" is received, it attempts emit the
signal to the GeoclueMasterClient, in the function position_provider_changed().
 If the client is destroyed by then, the memory it points to could be anything.
 Thus causing at times GLib-GObject warning or possibly even a crasher.

I have downloaded the original source and updated the function finalize
(GObject *object) as follows:

    finalize (GObject *object) 
    {
    GeoclueMasterClientPrivate* priv = GET_PRIVATE(object);
    dbus_g_proxy_disconnect_signal(priv->proxy, "PositionProviderChanged",
                                 G_CALLBACK (position_provider_changed),
                                 object);

    G_OBJECT_CLASS (geoclue_master_client_parent_class)->finalize (object);
    }

After this change, the crasher experienced by my application no longer exist
and the warning messages also disappeared.

For more detail, I have previously submitted a defect in Meego Bugzilla under: https://bugs.meego.com/show_bug.cgi?id=17918

All related attachments and detail can be retrieved from there.  

Thanks.