fix(css): loadPreprocessor tolerate require.resolve.paths not exists

[antfu]

Description

In some cases, require.resolve.paths does not exist (not yet sure why, might be some registers) and causing the package failed to resolve. This PR fix it as a workaround.

Additional context

Close #4557
Close nuxt/vite#162

What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

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• Read the Contributing Guidelines.
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