pgsql: Use NULL instead of 0 for pointer arguments.

Use NULL instead of 0 for pointer arguments.

Commit 5fe08c006c fixed this for calls to dshash_create().  This
commit fixes calls to dshash_attach() and dsa_create_in_place().

Reviewed-by: Masahiko Sawada <sawada.mshk@gmail.com>
Reviewed-by: Michael Paquier <michael@paquier.xyz>
Discussion: https://postgr.es/m/aECi_gSD9JnVWQ8T%40nathan

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/a31767fc0935bf8dce884ed35dbe644516d0115e

Modified Files
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src/backend/replication/logical/launcher.c | 2 +-
src/backend/utils/activity/pgstat_shmem.c  | 5 +++--
2 files changed, 4 insertions(+), 3 deletions(-)