[24.1] Fix file source search query with empty string value

[davelopez]

Follow-up to #18059

Providing query="" as a parameter was constructing the wrong filter "**". Also supports was passed to the file source as a keyword parameter in some circumstances but shouldn't.

Detected in https://github.com/galaxyproject/galaxy/actions/runs/9172325561/job/25219112137?pr=18059

How to test the changes?

• [x] I've included appropriate automated tests.
• [ ] This is a refactoring of components with existing test coverage.
• [ ] Instructions for manual testing are as follows:
  1. [add testing steps and prerequisites here if you didn't write automated tests covering all your changes]

License

• [x] I agree to license these and all my past contributions to the core galaxy codebase under the MIT license.