AvatarChooser: don't set contact_factory to NULL after unreffing.
AvatarChooser: don't set contact_factory to NULL after unreffing.

The object is being destroyed anyway.

svn path=/trunk/; revision=1692

Distrotech/telepathy-account-widgets,GNOME/telepathy-account-widgets,GNOME/telepathy-account-widgets,Distrotech/telepathy-account-widgets,GNOME/telepathy-account-widgets