It raises baseBuiltinFunc.vecEvalString() should never be called when using tiflash engine

[lilinghai]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

create table t(a int primary key,b int);
alter table t set tiflash replica 1;
insert into t values(1,2);
select  count(*) from t group by a having not case when null then max(null) end;

2. What did you expect to see? (Required)

successfully

3. What did you see instead (Required)

ERROR 1105 (HY000): baseBuiltinFunc.vecEvalString() should never be called, please contact the TiDB team for help

4. What is your TiDB version? (Required)

Release Version: v4.0.0-beta.2-2671-g3ec37294f
Edition: Community
Git Commit Hash: 3ec3729
Git Branch: master
UTC Build Time: 2021-04-16 16:57:55
GoVersion: go1.13
Race Enabled: false
TiKV Min Version: v3.0.0-60965b006877ca7234adaced7890d7b029ed1306
Check Table Before Drop: false

[cosven]

/severity moderate
/sig execution