[INLONG-11658][Sort] Fix the NPE of the Kafka sink error log for some exceptions without metadata information

[vernedeng]

Fixes #11658

Motivation

Modifications

Verifying this change

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• This change is a trivial rework/code cleanup without any test coverage.

• This change is already covered by existing tests, such as:
  (please describe tests)

• This change added tests and can be verified as follows:

  (example:)

  • Added integration tests for end-to-end deployment with large payloads (10MB)
  • Extended integration test for recovery after broker failure

Documentation

• Does this pull request introduce a new feature? (yes / no)
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