Fix annotation for bind_model()
Fix annotation for bind_model()

The (optional) annotation should only be used for (out) arguments; in
arguments that can be NULL should use the (nullable) annotation.

GNOME/clutter,Distrotech/clutter,Distrotech/clutter,Distrotech/clutter,GNOME/clutter,GNOME/clutter,GNOME/clutter,Distrotech/clutter,Distrotech/clutter,GNOME/clutter,Distrotech/clutter