Bug #28526 Correlated subquery with GROUP BY on outer query returns no results in 5.0.40+

Description:
This appears to be a regression in 5.0.40 relative to 5.0.38.

On MySQL 5.0.38, the following returns one row as I would expect, while on 5.0.40, 5.0.41 and the 5.0.42-20070517 snapshot it returns none.

CREATE TABLE subquery_bug_test (ref BIGINT not null, location BIGINT not null); 

-- Note that having two rows with the same "location" field
-- is necessary for the bug to manifest.
INSERT INTO subquery_bug_test (ref, location) VALUES (1,2);
INSERT INTO subquery_bug_test (ref, location) VALUES (3,2);

-- Returns one row on 5.0.38 but none on 5.0.40+
-- (yes, the two "location=" clauses are superfluous, but
-- the "location=2" one was originally an IN clause with several values -- this
-- is heavily stripped down)

SELECT location FROM subquery_bug_test AS a
  WHERE location=2
    AND location=( SELECT location FROM subquery_bug_test AS b
                     WHERE a.ref=b.ref
                       AND b.location=2
                     LIMIT 1 )
  GROUP BY location;

Initially I thought this might be the same issue as bug #27333, but applying the proposed patch for that bug doesn't appear to fix the problem.

How to repeat:
Run the above SQL fragment on one of the affected versions of the MySQL server.

verified exactly as described in initial report. >=5.0.40 returned 0 rows, < 5.0.40 returned 1 row.

mysql> select version();
+--------------+
| version()    |
+--------------+
| 5.0.42-debug |
+--------------+

<cut>

mysql> SELECT location FROM subquery_bug_test AS a
    ->   WHERE location=2
    ->     AND location=( SELECT location FROM subquery_bug_test AS b
    ->                      WHERE a.ref=b.ref
    ->                        AND b.location=2
    ->                      LIMIT 1 )
    ->   GROUP BY location;
Empty set (0.03 sec)

------------------

mysql> select version();
+--------------------------+
| version()                |
+--------------------------+
| 5.0.36-enterprise-gpl-nt |
+--------------------------+
1 row in set (0.00 sec)

<cut>

mysql> SELECT location FROM subquery_bug_test AS a
    ->   WHERE location=2
    ->     AND location=( SELECT location FROM subquery_bug_test AS b
    ->                      WHERE a.ref=b.ref
    ->                        AND b.location=2
    ->                      LIMIT 1 )
    ->   GROUP BY location;
+----------+
| location |
+----------+
|        2 |
+----------+
1 row in set (0.00 sec)

This bug is a duplicate of bug #28337 which is already fixed:

mysql> SELECT VERSION();
+--------------+
| VERSION()    |
+--------------+
| 5.0.44-debug |
+--------------+
1 row in set (0.00 sec)

mysql> CREATE TABLE subquery_bug_test (ref BIGINT not null, location BIGINT not null);
Query OK, 0 rows affected (0.49 sec)

mysql> INSERT INTO subquery_bug_test (ref, location) VALUES (1,2);
Query OK, 1 row affected (0.00 sec)

mysql> INSERT INTO subquery_bug_test (ref, location) VALUES (3,2);
Query OK, 1 row affected (0.00 sec)

mysql>
mysql> SELECT location FROM subquery_bug_test AS a
    ->   WHERE location=2
    ->     AND location=( SELECT location FROM subquery_bug_test AS b
    ->                      WHERE a.ref=b.ref
    ->                        AND b.location=2
    ->                      LIMIT 1 )
    ->   GROUP BY location;
+----------+
| location |
+----------+
|        2 |
+----------+
1 row in set (0.01 sec)