Empty networks don't have anything (besides lo) for us to dump and restore,
so we should allow these as well.
Reported-by: Dietmar Maurer <dietmar@proxmox.com>
Signed-off-by: Tycho Andersen <tycho.andersen@canonical.com>
Acked-by: Serge E. Hallyn <serge.hallyn@ubuntu.com>