return false if no slots found using slotExists()

[shaal]

Description

slotExists() returns empty array (which is truthy), that can be confusing when components trying to check if a slot exist or not. This PR (already in latest Outline codebase) return false if the slot does not exist.

Fixes # (issue)

Type of change

Please delete options that are not relevant.

• [x] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] This change requires a documentation update

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration

• [ ] Visual Testing
• [ ] Automated Testing
• [ ] Accessibility Testing

Checklist

• [ ] My code follows the style guidelines of this project
• [ ] I have performed a self-review of my own code
• [ ] I have commented my code, particularly in hard-to-understand areas
• [ ] I have made corresponding changes to the documentation
• [ ] My changes generate no new warnings
• [ ] I have added tests that prove my fix is effective or that my feature works
• [ ] New and existing unit tests pass locally with my changes
• [ ] Any dependent changes have been merged and published in downstream modules

[changeset-bot[bot]]

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Latest commit: 32bf01c96b5fd1091ea70c8a8d33eb52a40a5d96

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