worker will panic when sync an unsupported upstream

[lance6716]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. What did you do? If possible, provide a recipe for reproducing the error.

there's a table with DATETIME column of MariaDB 10.0.10 (which will not pass version check)

2. What did you expect to see?

create a task with version check skippped at that source and specify don't sync that table. works well

3. What did you see instead?

worker panic

may be fixed by #924

[lance6716]

all MariaDB releases could be found here

https://downloads.mariadb.org/mariadb/+releases/

[lance6716]

case 1:

1. start a 10.0.10 MariaDB
2. start a task with ignore-checking-items: ["version"]
3. create table t (c int primary key, c2 datetime(3));
4. insert into t values(1, '2021-05-19 10:38:40.759');
5. worker panic