CrossEngineSupport can not retrieve multi byte fields normally

When the CrossEngineSupport is enabled, we can run the SQL on two tables with different engine type(ColumnStore, MyISAM) but the results is not normal.

CREATE TABLE `test_cs` (
`c1` int(11) DEFAULT NULL,
`c2` varchar(64) DEFAULT NULL
) ENGINE=Columnstore DEFAULT CHARSET=utf8;

CREATE TABLE `test_myisam` (
`c1` int(11) DEFAULT NULL,
`c2` varchar(64) DEFAULT NULL
) ENGINE=MyISAM DEFAULT CHARSET=utf8;

insert into test.test_cs values(1, 'cs测试');
insert into test.test_myisam values(2, 'myisam测试');

select * from test.test_cs union select * from test.test_myisam;

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2 rows in set (0.14 sec)

It seems that the data of MyISAM table is not normal.