pgsql: Consistently set all fields in pg_stat_replication to null inste

Consistently set all fields in pg_stat_replication to null instead of 0

Previously the "sent" field would be set to 0 and all other xlog
pointers be set to NULL if there were no valid values (such as when
in a backup sending walsender).

Branch
------
master

Details
-------
http://git.postgresql.org/pg/commitdiff/a91bdf67c49ade2bdf6474607b64f9f0083db4a6

Modified Files
--------------
src/backend/replication/walsender.c |    3 +++
1 file changed, 3 insertions(+)