result may be wrong if there's a limit without order by placed above outer join

[winoros]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

create table t(a int, primary key (a));
insert into t values(1), (2);
select * from t t1 left join t t2 on t1.a=t2.a limit 1, 1;

2. What did you expect to see? (Required)

one row output

3. What did you see instead (Required)

empty

4. What is your TiDB version? (Required)

current master