pagila=> select last_value from actor_actor_id_seq;
ERROR:  permission denied for sequence actor_actor_id_seq

pagila=> select case when false then (select last_value from actor_actor_id_seq) else null end;
 case
------

(1 row)

pagila=> select pg_catalog.has_sequence_privilege('actor_actor_id_seq'::regclass,'SELECT,USAGE'::text);                      has_sequence_privilege
------------------------
 f
(1 row)

pagila=> select case when pg_catalog.has_sequence_privilege('actor_actor_id_seq'::regclass,'SELECT,USAGE'::text) then (select last_value from actor_actor_id_seq) else null end;
ERROR:  permission denied for sequence actor_actor_id_seq