Adding a DNS zone on a slave throws an error

When adding a new zone to a slave I always get two errors mailed.

WARNING - Reason for Bind restart failure: zone example.com/IN: has no NS records
zone example.com/IN: not loaded due to errors.

WARNING - Writing BIND domain file failed: /etc/bind/master/example.com zone example.com/IN: has no NS records zone example.com/IN: not loaded due to errors.

The reason seems to be that the first named-checkzone is called just after the dns_soa record is replicated, but before any of the dns_rr records are replicated.

The easiest fix seems to be to just skip rendering and reloading bind if there are no records.

MR coming...