gdbus function call on interface NULL does not work

[Bernhard Schuster <schuster bernhard googlemail com>]

I created a demo which shows that remote method calls on interface NULL do not work with `g_dbus_connection_register_object`. According to http://dbus.freedesktop.org/doc/api/html/group__DBusMessage.html#ga6c8a4c5d350c1962b11300cc4dd0c2e2 the spec says that this is explicitly allowed for method calls.

A quick and dirty showcase, the ref implementation does recognize the method call on iface null, whereas the gdbus implentation fails.

Get it from github https://github.com/drahnr/gdbus-demo

I guess this is a bug...

Best

Bernhard