Fix check for undefined-ness of LastPlainCounters
Fix check for undefined-ness of LastPlainCounters

Change-Id: I194a91cdc9ab83826af2a36473302f4e97e75c78
Reviewed-on: http://review.couchbase.org/72339
Tested-by: Aliaksey Artamonau <3c875bcfb3adf2a65b2ae7686ca921e6c9433147@gmail.com>
Reviewed-by: Artem Stemkovski <15a0730a27c69f62ab86f2b6c639fca202166c02@couchbase.com>

membase/ns_server,membase/ns_server,ceejatec/ns_server,membase/ns_server,membase/ns_server,membase/ns_server,membase/ns_server,ceejatec/ns_server,ceejatec/ns_server,ceejatec/ns_server,ceejatec/ns_server,ceejatec/ns_server