expression: fix approx_percent panic on bit column (#23687)

[ti-srebot]

cherry-pick #23687 to release-4.0
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# In tidb repo:
git pr https://github.com/pingcap/tidb/pull/23702

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git push [email protected]:ti-srebot/tidb.git pr/23702:release-4.0-c32895f66741

---

Signed-off-by: lzmhhh123 [email protected]

What problem does this PR solve?

Issue Number: close #23662

What is changed and how it works?

How it Works:

Related changes

• PR to update pingcap/docs/pingcap/docs-cn:
• Need to cherry-pick to the release branch

Check List

Tests

• Unit test
• Integration test

Release note

• fix approx_percent panic on bit column

[ti-srebot]

/run-all-tests

[ti-srebot]

@lzmhhh123 you're already a collaborator in bot's repo.

[ichn-hu]

@tangenta PTAL

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• ichn-hu
• qw4990

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[qw4990]

/merge

[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: e720516

[ti-chi-bot]

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