pgsql: Fix handling of pgbench's hash when no argument is provided

Fix handling of pgbench's hash when no argument is provided

Depending on the platform used, this can cause a crash in the worst
case, or an unhelpful error message, so fail gracefully.

Author: Fabien Coelho
Discussion: https://postgr.es/m/alpine.DEB.2.21.1807262302550.29874@lancre
Backpatch: 11-, where hash() has been added in pgbench.

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/39d51fe87dae843574fa2349128679800bfe7ccd

Modified Files
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src/bin/pgbench/exprparse.y                |  2 +-
src/bin/pgbench/t/002_pgbench_no_server.pl | 20 ++++++++++++++++++++
2 files changed, 21 insertions(+), 1 deletion(-)