fix: reset search mini-form when we have no data / an empty response

[DanielRuf]

Description

Currently the search form does not reset the results when we have no result / data.

Fixed Issues (if relevant)

Manual testing scenarios

1. go to http://mag2opensource.basecom.de/catalogsearch/result/?q=pullover
2. write pullover in the search
3. autocomplete with result number appears
4. now append en so we have pulloveren
5. autocomplete still shows the results

Contribution checklist

• Pull request has a meaningful description of its purpose
• All commits are accompanied by meaningful commit messages
• All new or changed code is covered with unit/integration tests (if applicable)
• All automated tests passed successfully (all builds on Travis CI are green)

[magento-engcom-team]

Hi @DanielRuf. Thank you for your contribution
Here is some useful tips how you can test your changes using Magento test environment.
Add the comment under your pull request to deploy test or vanilla Magento instance:

• @magento-engcom-team give me test instance - deploy test instance based on PR changes
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[phoenix128]

@magento-engcom-team give me test instance

[magento-engcom-team]

Hi @phoenix128. Thank you for your request. I'm working on Magento instance for you

[magento-engcom-team]

Hi @phoenix128, here is your new Magento instance.
Admin access: https://pr-18055.engcom.dev.magento.com/admin
Login: admin Password: 123123q

[phoenix128]

Hello @DanielRuf ;
thank you for this contribution and for your ime, please check my review.

[magento-engcom-team]

Hi @phoenix128, thank you for the review.
ENGCOM-2995 has been created to process this Pull Request

[magento-engcom-team]

Hi @DanielRuf. Thank you for your contribution.
We will aim to release these changes as part of 2.2.8.
Please check the release notes for final confirmation.

Please, consider to port this solution to 2.3 release line.
You may use Porting tool to port commits automatically.