glib: fix NRE regression after interface naming changed

ListBase was throwing a NullReferenceException in DataMarshal() due
to the fact that Reflection was being used to find the adapter name
of the interface generated by the bindings, which has recently
changed [1].

[1] https://github.com/mono/gtk-sharp/commit/6cb03440c1a3fb52c23d5d681e44f772d687333c