Wrong query results when `using index for group-by`

select @@SQL_MODE;

+-------------------------------------------------------------------------------------------+

| @@SQL_MODE                                                                                |

+-------------------------------------------------------------------------------------------+

| STRICT_TRANS_TABLES,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION |

+-------------------------------------------------------------------------------------------+

1 row in set (0.000 sec)

select @@GLOBAL.SQL_MODE;

+-------------------------------------------------------------------------------------------+

| @@GLOBAL.SQL_MODE                                                                         |

+-------------------------------------------------------------------------------------------+

| STRICT_TRANS_TABLES,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION |

+-------------------------------------------------------------------------------------------+

1 row in set (0.000 sec)

/* create the database */

CREATE DATABASE IF NOT EXISTS bug_investigation;

use bug_investigation;

/* create the table */

DROP TABLE IF EXISTS `cats`;

CREATE TABLE `cats` (

  `id` int(11) NOT NULL AUTO_INCREMENT,

  `owner_id` int(11) DEFAULT NULL,

  `foo` tinyint(1) DEFAULT 0,

  `whatever` varchar(255) DEFAULT NULL,

  PRIMARY KEY (`id`),

  KEY `index_cats_on_owner_id_and_foo` (`owner_id`,`foo`)

) ENGINE=InnoDB DEFAULT CHARSET=utf8;

/* Insert data */

INSERT INTO cats (owner_id, foo, whatever) VALUES (1, TRUE, "yello");

INSERT INTO cats (owner_id, foo, whatever) VALUES (1, FALSE, "yello");

INSERT INTO cats (owner_id, foo, whatever) VALUES (2, TRUE, "yello");

INSERT INTO cats (owner_id, foo, whatever) VALUES (2, TRUE, "yello");

INSERT INTO cats (owner_id, foo, whatever) VALUES (2, FALSE, "yello");

SELECT * FROM cats;

+----+----------+------+----------+

| id | owner_id | foo  | whatever |

+----+----------+------+----------+

|  1 |        1 |    1 | yello    |

|  2 |        1 |    0 | yello    |

|  3 |        2 |    1 | yello    |

|  4 |        2 |    1 | yello    |

|  5 |        2 |    0 | yello    |

+----+----------+------+----------+

5 rows in set (0.001 sec)

SELECT DISTINCT owner_id FROM cats WHERE foo = true GROUP BY owner_id HAVING (COUNT(*) = 1);

MariaDB [bug_investigation]> SELECT DISTINCT owner_id FROM cats WHERE foo = true GROUP BY owner_id HAVING (COUNT(*) = 1);

+----------+

| owner_id |

+----------+

|        1 |

+----------+

1 row in set (0.000 sec)

MariaDB [bug_investigation]> EXPLAIN SELECT DISTINCT owner_id FROM cats WHERE foo = true GROUP BY owner_id HAVING (COUNT(*) = 1);

+------+-------------+-------+-------+---------------+--------------------------------+---------+------+------+--------------------------+

| id   | select_type | table | type  | possible_keys | key                            | key_len | ref  | rows | Extra                    |

+------+-------------+-------+-------+---------------+--------------------------------+---------+------+------+--------------------------+

|    1 | SIMPLE      | cats  | index | NULL          | index_cats_on_owner_id_and_foo | 7       | NULL |    5 | Using where; Using index |

+------+-------------+-------+-------+---------------+--------------------------------+---------+------+------+--------------------------+

1 row in set (0.001 sec)

MariaDB [bug_investigation]> SELECT DISTINCT owner_id FROM cats WHERE foo = true GROUP BY owner_id HAVING (COUNT(*) = 1);

Empty set (0.000 sec)

MariaDB [bug_investigation]> EXPLAIN SELECT DISTINCT owner_id FROM cats WHERE foo = true GROUP BY owner_id HAVING (COUNT(*) = 1);

+------+-------------+-------+-------+---------------+--------------------------------+---------+------+------+---------------------------------------+

| id   | select_type | table | type  | possible_keys | key                            | key_len | ref  | rows | Extra                                 |

+------+-------------+-------+-------+---------------+--------------------------------+---------+------+------+---------------------------------------+

|    1 | SIMPLE      | cats  | range | NULL          | index_cats_on_owner_id_and_foo | 7       | NULL | 6    | Using where; Using index for group-by |

+------+-------------+-------+-------+---------------+--------------------------------+---------+------+------+---------------------------------------+

1 row in set (0.001 sec)

MariaDB [bug_investigation]> SELECT DISTINCT owner_id FROM cats IGNORE INDEX (index_cats_on_owner_id_and_foo) WHERE foo = true GROUP BY owner_id HAVING (COUNT(*) = 1);

+----------+

| owner_id |

+----------+

|        1 |

+----------+

1 row in set (0.000 sec)