Submitted by: @dyemanov

Is related to QA434

Test case:

recreate table bugtest (id int)
insert into bugtest (id) values (123)

recreate procedure p_bugtest (in_id int)
returns (cnt int)
as
declare predicate varchar(1000);
begin
if (:in_id is null) then
predicate = ' ? is null';
else
predicate = ' id = ?';

execute statement ('select count(*) from bugtest where' || predicate) (:in_id)
into :cnt;
end

execute procedure p_bugtest (123)
-- cnt = 1
execute procedure p_bugtest (null)
-- cnt = 1
execute procedure p_bugtest (123)
-- cnt = 0 !!!

Commits: fd04d5f 1ef4fd6