[playground] Fix syntax error from crashing the Compiler playground (#34623)

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## Summary

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Fixes a syntax error causing the Compiler playground to crash. Resolves
https://github.com/facebook/react/issues/34622.

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Tested locally and added a test.

<img width="1470" height="836" alt="Screenshot 2025-09-27 at 8 13 07 AM"
src="https://github.com/user-attachments/assets/29473682-94c3-49dc-9ee9-c2004062aaea"
/>