chore: add default case

[namkyu1999]

Proposed changes

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Types of changes

What types of changes does your code introduce to Litmus? Put an x in the boxes that apply

• [ ] New feature (non-breaking change which adds functionality)
• [ ] Bugfix (non-breaking change which fixes an issue)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] Documentation Update (if none of the other choices applies)

Checklist

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• [ ] I have read the CONTRIBUTING doc
• [ ] I have signed the commit for DCO to be passed.
• [ ] Lint and unit tests pass locally with my changes
• [ ] I have added tests that prove my fix is effective or that my feature works (if appropriate)
• [ ] I have added necessary documentation (if appropriate)

Dependency

• Please add the links to the dependent PR need to be merged before this (if any).

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