fix: potential null dereference in react compiler configuration (#32571)

[zendy199x]

Fixes #32571

Summary

Fix potential null dereference in React Compiler configuration by adding a null check for the plugins array.

The babel.config-react-compiler.js file contains a hack comment about Zod spreading values in React Compiler's build artifact. If the baseConfig.plugins array is null or undefined, the assignment plugins: baseConfig.plugins will cause a runtime TypeError when the compiler tries to process the configuration. This could crash the build process or cause incorrect transpilation.

How did you test this change?

• Modified the babel.config-react-compiler.js file to add a null check before assigning plugins
• Verified the change prevents TypeError when baseConfig.plugins is null or undefined
• Confirmed the build process continues to work correctly with valid plugin arrays

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[Copilot]

Pull request overview

This PR adjusts the React Compiler Babel config used for transforming the compiler’s build artifact during Jest runs, ensuring the exported plugins field is always an array to avoid runtime failures when baseConfig.plugins is missing or invalid.

Changes:

• Guard plugins in babel.config-react-compiler.js with an Array.isArray check and default to [].

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[Copilot]

This fallback will silently drop plugins if baseConfig.plugins is anything other than an array (e.g. a function/object due to a future change), which could lead to the compiler artifact being transformed incorrectly while tests still run. Consider only defaulting for null/undefined and throwing a clear error for other unexpected types so misconfiguration fails fast with a helpful message.

[Copilot]

PR description mentions crashing the build process, but this config appears to be used only by Jest (see scripts/jest/config.base.js transform for the compiler dist file). Consider updating the PR summary/testing notes to reflect that the impact is on local/test transforms rather than the production build, unless there are other consumers not found in-repo.

[zendy199x]

I took another pass at the failing CI checks, but after 1 follow-up attempt(s) these checks are still failing: Cleanup artifacts.

I'm closing this PR for now because the remaining failures look like they need manual investigation before the change can move forward.

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