executor: fix load data panic if the data is broken at escape character (#30868)

[ti-srebot]

cherry-pick #30868 to release-5.4
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# In tidb repo:
git pr https://github.com/pingcap/tidb/pull/31774

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---

What problem does this PR solve?

Issue Number: close #31589

Problem Summary:

What is changed and how it works?

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No code

Release note

fix load data will panic in some case

[ti-chi-bot]

[REVIEW NOTIFICATION]

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• Defined2014
• youjiali1995

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[ti-srebot]

/run-all-tests

[ti-srebot]

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

[purelind]

/run-mysql-test

[xiongjiwei]

/merge

[ti-chi-bot]

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

Commit hash: 6947622

[ti-chi-bot]

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