hint: fix panic when query block not found in prepare statement (#46818)

[ti-chi-bot]

This is an automated cherry-pick of #46818

What problem does this PR solve?

Issue Number: close #46817

Problem Summary:

What is changed and how it works?

Fix it.

Check List

Tests

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

Side effects

• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Breaking backward compatibility

Documentation

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features
• Changes MySQL compatibility

Release note

Please refer to Release Notes Language Style Guide to write a quality release note.

None

[ti-chi-bot]

This cherry pick PR is for a release branch and has not yet been approved by release team.
Adding the do-not-merge/cherry-pick-not-approved label.

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2023-09-11 05:12:22.846009046 +0000 UTC m=+246124.770565426: ☑️ agreed by jackysp.
• 2023-10-17 14:02:32.618525498 +0000 UTC m=+1752150.205635642: ☑️ agreed by chrysan.

[chrysan]

/retest-required

[chrysan]

/test unit-test

[tiprow]

@chrysan: No presubmit jobs available for pingcap/tidb@release-6.5

In response to this:

/test unit-test

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[chrysan]

/approve

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: chrysan, jackysp

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• OWNERS [chrysan,jackysp]

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[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (release-6.5@0ba0a82). Click here to learn what that means.
The diff coverage is n/a.

Additional details and impacted files

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