mysql数据库在使用过程中user表中突然多了两个user为空的记录，如下：

mysql> select Host, user,password from user;
+-----------+--------+-------------------------------------------+
| Host      | user   | password                                  |
+-----------+--------+-------------------------------------------+
| localhost | root   | * xxxxxxxxxxxxxxxx |
| abcde     | root   | * xxxxxxxxxxxxxxxx |
| 127.0.0.1 | root   | * xxxxxxxxxxxxxxxx |
| localhost |        |                                           |
| abcde     |        |                                           |
| %         | root   | * xxxxxxxxxxxxxxxx |
| %         | server | * xxxxxxxxxxxxxxxx |
+-----------+--------+-------------------------------------------+

这两条user为空的记录是怎么产生的？