pgsql: Fix pgbench in prepared mode with an empty pipeline

Fix pgbench in prepared mode with an empty pipeline It crashes because it references memory that's not allocated in that particular case. Fix by allocating it. Reported-by: Alexander Lakhin Discussion: https://postgr.es/m/bcf802a6-afc1-95b9-7bf4-c5dd868ec...@gmail.com Branch -- master Det

pgsql: Fix pgbench in prepared mode with an empty pipeline

Fix pgbench in prepared mode with an empty pipeline It crashes because it references memory that's not allocated in that particular case. Fix by allocating it. Reported-by: Alexander Lakhin Discussion: https://postgr.es/m/bcf802a6-afc1-95b9-7bf4-c5dd868ec...@gmail.com Branch -- REL_15_STAB