expression: Fix wrong way to check for overflow (#27122)

[ti-srebot]

cherry-pick #27122 to release-5.1
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/27418

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

git push git@github.com:ti-srebot/tidb.git pr/27418:release-5.1-949dafb35c65

---

What problem does this PR solve?

Issue Number: close #26977

Tests

• Unit test

Release note

None

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• ichn-hu
• wshwsh12

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[ti-srebot]

/run-all-tests

[ti-srebot]

@ichn-hu you're already a collaborator in bot's repo.

[zhouqiang-cl]

/merge

[ti-chi-bot]

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

Commit hash: d92388c

[ti-chi-bot]

@ti-srebot: Your PR was out of date, I have automatically updated it for you.

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/run-all-tests

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