LP:965950 - left join lead to crash (in case of converting it to inner join)

This test suite crashes:

create table t1 (a int, b int);
insert into t1 values (1,1),(2,2);
create table t2 (a int, b int);
insert into t2 values (1,1),(2,2);

select t1.b, t2.b from t1 left join t2 on (t2.a=t1.a) where t2.a > 5;

drop table t1, t2;