CONNECT PIVOT impossible when columns contain NULL

mysql 10.0.10-MariaDB (root) [test]> show create table t1\G

*************************** 1. row ***************************

       Table: t1

Create Table: CREATE TABLE `t1` (

  `id` int(10) unsigned NOT NULL AUTO_INCREMENT,

  `c1` char(32) DEFAULT NULL,

  `c2` char(32) DEFAULT NULL,

  `c3` char(32) DEFAULT NULL,

  PRIMARY KEY (`id`)

) ENGINE=InnoDB AUTO_INCREMENT=2 DEFAULT CHARSET=latin1

1 row in set (0.00 sec)

mysql 10.0.10-MariaDB (root) [test]> select * from t1;

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

| id | c1   | c2   | c3   |

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

|  1 | a    | NULL | c    |

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

1 row in set (0.00 sec)

mysql 10.0.10-MariaDB (root) [test]> create table t1_pivot engine=connect table_type=pivot tabname=t1;

ERROR 1939 (HY000): Engine CONNECT failed to discover table `test`.`t1_pivot` with 'CREATE TABLE whatever (`id` INT(10) NOT NULL,`c1` CHAR(32) NOT NULL,`` CHAR(32) NOT NULL FLAG=1) TABLE_TYPE='pivot' TABNAME='t1''