wrong result when aggregation on partition table

[time-and-fate]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

use test;
create table t(a int, b int, c int, d int) partition by range columns(d) ( partition p0 values less than (20), partition p1 values less than(40), partition p2 values less than(60));
insert into t values(1,1,1,1), (2,2,2,2), (22,22,22,22), (44,44,44,44);
set sql_mode='';
select count(*) from (select a, b from t where d > 1 and d < 60 and b > 0 group by b, c) tt;

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

+----------+
| count(*) |
+----------+
|        3 |
+----------+
1 row in set (0.007 sec)

3. What did you see instead (Required)

ERROR 1105 (HY000): Internal error: UnionExec chunk column count mismatch, req: 3, result: 2

4. What is your TiDB version? (Required)

release 5.0, release 5.1, release 5.2, master

[time-and-fate]

Duplicated with #26554

[github-actions]

Please check whether the issue should be labeled with 'affects-x.y' or 'backport-x.y.z',
and then remove 'needs-more-info' label.

[time-and-fate]

/unlabel needs-more-info

[time-and-fate]

/remove-label needs-more-info

[ti-chi-bot]

@time-and-fate: The label(s) needs-more-info cannot be applied. These labels are supported: CHANGELOG, challenge-program, compatibility-breaker, contribution, correctness, first-time-contributor, good-first-issue, hacktoberfest, high-performance, hptc, need-more-info, needs-cherry-pick-3.0, needs-cherry-pick-3.1, needs-cherry-pick-4.0, needs-cherry-pick-5.0, needs-cherry-pick-5.1, needs-cherry-pick-5.2, proposal, release-note, require-LGT3, security, tools.

In response to this:

/remove-label needs-more-info

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