dumpling: fix panic when query result is empty

[D3Hunter]

What problem does this PR solve?

Issue Number: close #45200

Problem Summary:

What is changed and how it works?

• revert some code in dumpling: fix dumpling panic bug when --output-file-template is incorrect #41588, we still init SQLRowIter lazily, and check it on close

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

[tiprow]

Hi @D3Hunter. Thanks for your PR.

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[D3Hunter]

/ok-to-test

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: lance6716, lichunzhu

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2023-07-07 04:01:12.173488207 +0000 UTC m=+45363.943826919: ☑️ agreed by lichunzhu.
• 2023-07-10 05:06:10.634702268 +0000 UTC m=+308462.405040979: ☑️ agreed by lance6716.

[D3Hunter]

/retest

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-7.1: #45258.