kerberos: fix leak in register_error_domain
kerberos: fix leak in register_error_domain

In the event a type was not known, we were leaking the
type name.

https://bugzilla.gnome.org/show_bug.cgi?id=726353

Distrotech/gnome-online-accounts,ritzk/gnome-online-accounts,Distrotech/gnome-online-accounts,dnohales/gnome-online-accounts,dnohales/gnome-online-accounts,halfline/gnome-online-accounts,felipeborges/gnome-online-accounts,ritzk/gnome-online-accounts,felipeborges/gnome-online-accounts,halfline/gnome-online-accounts,dnohales/gnome-online-accounts,halfline/gnome-online-accounts,felipeborges/gnome-online-accounts,Distrotech/gnome-online-accounts,ritzk/gnome-online-accounts