fix: search box does not work when themeConfig search provider is set

[jooy2]

Pull request checklist

You should familiarize yourself with the files README.md, CONTRIBUTING.md, and CODE_OF_CONDUCT.md in the root of your project.

• If an issue has been created for this, add (fixes #{ISSUE_NUMBER}) to the end of the commit description. In {ISSUE_NUMBER}, please include the relevant issue number.
• If you need to update or add to the article, please update the relevant content. If a multilingual article exists, you should update all relevant content in your own language, except for translations.
• Add or update test code if it exists and is needed. Also, verify that the tests pass.
• If this PR is not yet complete, keep the PR in draft status. If it's no longer valid, close the PR with an explanation.

What did you change?

fix search box does not work when themeConfig search provider is set

fixes #9