pgsql: Don't abort pg_basebackup when receiving empty WAL block

Don't abort pg_basebackup when receiving empty WAL block

This can happen exactly at the switch of a logical WAL file
(segment number ending in FE), when running pg_basebackup connected
to a standby server, and would cause the backup to abort with
the error message "streaming header too small".

There is nothing wrong with an empty message, it's just unnecessary,
and the rest of the code can handle the case of an empty message,
so this patch just removes the error condition when the size is
exactly zero.

Branch
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REL9_2_STABLE

Details
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http://git.postgresql.org/pg/commitdiff/c6ec8793aa59d1842082e14b4b4aae7d4bd883fd

Modified Files
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src/bin/pg_basebackup/receivelog.c |    2 +-
1 file changed, 1 insertion(+), 1 deletion(-)