Wrong result with subquery in SELECT clause, and constant table in main query and implicit grouping

[Timour Katchaounov]

The following test case, extracted from the test for bug lp:680846 produces wrong result:

CREATE TABLE t1 (f1 int) ;
INSERT INTO t1 VALUES (7),(8);

CREATE TABLE t2 (f2 int, f3 varchar(32)) ;
INSERT INTO t2 VALUES (1,'f');

SELECT COUNT(f2), (SELECT f1 FROM t1 WHERE t2.f2 limit 1) AS f4
FROM t2, t1
WHERE 'v'= t2.f3;

+-----------+------+
| COUNT(f2) | f4 |
+-----------+------+
| 0 | 7 |
+-----------+------+

The correct result is:

+-----------+------+
| COUNT(f2) | f4 |
+-----------+------+
| 0 | NULL |
+-----------+------+