The code handles this case correctly: we merely skip the loop. However it
is probably best to return an explicit error.

Reviewed-by: Eric Blake <eblake@redhat.com>
Acked-by: Mark Kanda <mark.kanda@oracle.com>
Signed-off-by: Eyal Moscovici <eyal.moscovici@oracle.com>
Message-Id: <20200513133629.18508-3-eyal.moscovici@oracle.com>
[eblake: commit message tweak]
Signed-off-by: Eric Blake <eblake@redhat.com>