fix(select): fetching options when some dependency is null

[vtsvetkov-splunk]

Issue number: ADDON-76586

PR Type

What kind of change does this PR introduce?

• [ ] Feature
• [x] Bug Fix
• [ ] Refactoring (no functional or API changes)
• [ ] Documentation Update
• [ ] Maintenance (dependency updates, CI, etc.)

Summary

Root cause

Regression from #1424. There was a Null Pointer Exception due to undefined values of dependencyValues and calling .toString() on undefined. NPE itself is not a problem since it is silenced, but the request is not made due to this and "No manches" is shown

Changes

• Filter out null and undefined values (as axios does)
• Add tests covering this bug

User experience

Ability to see options fetching from the server

Checklist

If an item doesn't apply to your changes, leave it unchecked.

• [x] I have performed a self-review of this change according to the development guidelines
• [x] Tests have been added/modified to cover the changes (testing doc)
• [ ] Changes are documented
• [x] PR title and description follows the contributing principles