BUG #6407: Crash on queries to gin index with multiply values

The following bug has been logged on the website:

Bug reference:      6407
Logged by:          Yury Don
Email address:      don@rosfirm.ru
PostgreSQL version: 9.1.2
Operating system:   Linux (Debian)
Description:=20=20=20=20=20=20=20=20

When making "in" query to fiels with gin index, server crashes. Below=20
create table tmp(id serial not null primary key, f1 integer, f2 text);
insert into tmp (f1,f2) values (1,'a'),(2,'b'),(3,'c');
create index tmp_f1_idx on tmp using gin (f1);
create index tmp_f2_idx on tmp using gin (f2);
set enable_seqscan to off;
select * from tmp where f1 in (1, 2);
After this query server chrashes:
server process (PID ...) was terminated by signal 11: Segmentation fault
The same after query on text field:
select * from tmp where f2 in ('a', 'd');