expression: ignore NULL in handle binary literal (#49527) (#49528)

[ti-chi-bot]

This is an automated cherry-pick of #49528

This is a manually cherry-pick of #49527

What problem does this PR solve?

Issue Number: close #49526

Problem Summary:

What changed and how does it work?

Ignore the TypeNull in HandleBinaryLiteral, as the castStringToString will actually do nothing for NULL (except changing the type).

Check List

Tests

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

  • I checked and no code files have been changed.

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

None

[ti-chi-bot]

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[ti-chi-bot]

@ti-chi-bot: The following tests failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
idc-jenkins-ci-tidb/unit-test	4d741d3	link	true	/test unit-test
idc-jenkins-ci-tidb/check_dev	4d741d3	link	true	/test check-dev

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