[Tests] Add unit tests for isEmpty object utility function

[gonzaloriestra]

Why are these changes needed?

The isEmpty function in packages/cli-kit/src/public/common/object.ts lacked direct unit test coverage in packages/cli-kit/src/public/common/object.test.ts.

How to test your changes?

CI

Checklist

• I have evaluated the impact of this change and attribute it to a domain.
• I have added description for changesets or explicitly marked as no changeset required
• I have updated the documentation if required
• I have added tests for the changes

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PR created automatically by Jules for task 487141054567347593 started by @gonzaloriestra

[google-labs-jules]

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