fix(css): avoid generating empty JS files when JS files becomes empty but has CSS files imported

[sapphi-red]

Description

fixes #6913 fixes https://github.com/vitejs/vite/issues/6913#issuecomment-1166462434 fixes #16582

Additional context

---

What is the purpose of this pull request?

• [x] Bug fix
• [ ] New Feature
• [ ] Documentation update
• [ ] Other

Before submitting the PR, please make sure you do the following

• [x] Read the Contributing Guidelines, especially the Pull Request Guidelines.
• [x] Check that there isn't already a PR that solves the problem the same way to avoid creating a duplicate.
• [x] Provide a description in this PR that addresses what the PR is solving, or reference the issue that it solves (e.g. fixes #123).
• [x] Update the corresponding documentation if needed.
• [x] Ideally, include relevant tests that fail without this PR but pass with it.

[bolt-new-by-stackblitz[bot]]

Run & review this pull request in StackBlitz Codeflow.

[sapphi-red]

/ecosystem-ci run

[vite-ecosystem-ci[bot]]

📝 Ran ecosystem CI on d8b81b4: Open

suite	result	latest scheduled
analogjs	:x: failure	:white_check_mark: success
nuxt	:x: failure	:white_check_mark: success
nx	:x: failure	:x: failure
vite-plugin-react-pages	:white_check_mark: success	:x: failure
vite-plugin-vue	:x: failure	:white_check_mark: success

:white_check_mark: astro, histoire, ladle, laravel, marko, previewjs, qwik, rakkas, sveltekit, unocss, vike, vite-plugin-pwa, vite-plugin-react, vite-plugin-react-swc, vite-plugin-svelte, vite-setup-catalogue, vitepress, vitest

[vite-ecosystem-ci[bot]]

📝 Ran ecosystem CI on d8b81b4: Open

suite	result	latest scheduled
nx	:x: failure	:x: failure
vite-plugin-react-pages	:white_check_mark: success	:x: failure

:white_check_mark: analogjs, astro, histoire, ladle, laravel, marko, nuxt, previewjs, qwik, rakkas, sveltekit, unocss, vike, vite-plugin-pwa, vite-plugin-react, vite-plugin-react-swc, vite-plugin-svelte, vite-plugin-vue, vite-setup-catalogue, vitepress, vitest

[susnux]

• Resolves https://github.com/vitejs/vite/issues/16582