pgsql: Fix copy-pasto in freeing memory on error in vacuumlo.

Fix copy-pasto in freeing memory on error in vacuumlo.

It's harmless to call PQfreemem() with a NULL argument, so the only
consequence was that if allocating 'schema' failed, but allocating 'table'
or 'field' succeeded, we would leak a bit of memory. That's highly
unlikely to happen, so this is just academical, but let's get it right.

Per bug #15838 from Timur Birsh. Backpatch back to 9.5, where the
PQfreemem() calls were introduced.

Discussion: https://www.postgresql.org/message-id/15838-3221652c72c5e69d@postgresql.org

Branch
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REL9_5_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/99b5ff2eaf4c64c6ac8204f622075d7f01ff4cc2

Modified Files
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contrib/vacuumlo/vacuumlo.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)