expression: do not adjust int when it is null and compared year (#22821)

[ti-srebot]

cherry-pick #22821 to release-4.0
You can switch your code base to this Pull Request by using git-extras:

# In tidb repo:
git pr https://github.com/pingcap/tidb/pull/22844

After apply modifications, you can push your change to this PR via:

git push git@github.com:ti-srebot/tidb.git pr/22844:release-4.0-4f56ab07a24e

---

Signed-off-by: lzmhhh123 lzmhhh123@gmail.com

What problem does this PR solve?

Issue Number: close #22817

What is changed and how it works?

How it Works: as the title says.

Related changes

• Need to cherry-pick to the release branch

Check List

Tests

• Unit test
• Integration test

Release note

• do not ajust int when it is null and compared year

[ti-srebot]

/run-all-tests

[ti-srebot]

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

[XuHuaiyu]

/lgtm

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• XuHuaiyu

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[XuHuaiyu]

/merge

[ti-chi-bot]

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

Commit hash: becc82a

[XuHuaiyu]

/lgtm

[ti-chi-bot]

@ti-srebot: Your PR was out of date, I have automatically updated it for you.

At the same time I will also trigger all tests for you:

/run-all-tests

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