Wrong result: HAVING evaluates NULL = NULL as true, SELECT from view returns extra rows

create or replace table t (a int);

insert into t values (1),(2);

create or replace view v as select if(a = 1,'Y','N') AS b from t;

select v2.b AS f from v v1 left join v v2 ON (false) having (f = f);

# With ORDER BY, result set is empty as expected

select v2.b AS f from v v1 left join v v2 ON (false) having (f = f) order by f;

# Cleanup

drop view v;

drop table t;

MariaDB [test]> select v2.b AS f from v v1 left join v v2 ON (false) having (f = f);

+------+

| f    |

+------+

| NULL |

| NULL |

+------+

2 rows in set (0.006 sec)

MariaDB [test]> select v2.b AS f from v v1 left join v v2 ON (false) having (f = f) order by f;

Empty set (0.002 sec)

MariaDB [test]> explain extended select v2.b AS f from v v1 left join v v2 ON (false) having (f = f);

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

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

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

|    1 | SIMPLE      | t     | ALL  | NULL          | NULL | NULL    | NULL | 2    |   100.00 |                                                 |

|    1 | SIMPLE      | t     | ALL  | NULL          | NULL | NULL    | NULL | 2    |   100.00 | Using where; Using join buffer (flat, BNL join) |

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

2 rows in set, 1 warning (0.001 sec)

MariaDB [test]> show warnings;

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

| Level | Code | Message                                                                                                            |

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

| Note  | 1003 | select if(`test`.`t`.`a` = 1,'Y','N') AS `f` from `test`.`t` left join (`test`.`t`) on(0) where 1 having `b` = `b` |

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

1 row in set (0.000 sec)