refactor: http handler check has_result_set() before get schema of plan.

[youngsofun]

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Summary

Briefly describe what this PR aims to solve. Include background context that will help reviewers understand the purpose of the PR.

• Fixes #[Link the issue here]

Tests

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• Logic Test
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• No Test - Explain why

Type of change

• Bug Fix (non-breaking change which fixes an issue)
• New Feature (non-breaking change which adds functionality)
• Breaking Change (fix or feature that could cause existing functionality not to work as expected)
• Documentation Update
• Refactoring
• Performance Improvement
• Other (please describe):

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