Fix crash when napi_register_module_v1 returns nullptr

[190n]

What does this PR do?

Ensures that if napi_register_module_v1 returns nullptr, we use the exports object as the return value of require(). This matches Node.js behavior.

Fixes #16766

How did you verify your code works?

• I included a test for the new code, or existing tests cover it
• I ran my tests locally and they pass (bun-debug test test-file-name.test)

[robobun]

^{Updated 7:53 PM PT - Jan 27th, 2025}

❌ @190n, your commit ad0b185 has 1 failures in Build #10678:

• test/cli/install/bun-install-registry.test.ts - 2 failing on 🪟 2019 x64

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🧪   try this PR locally:

bunx bun-pr 16816