fix(plugin-vue): handle sourcemap with empty script code

[edison1105]

Description

close vuejs/core#13260

• Before
• With this PR

Additional context

---

What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

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• Read the Contributing Guidelines.
• Read the Pull Request Guidelines and follow the PR Title Convention.
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commit: 30c5aa0

[sapphi-red]

I think the linked issue (vuejs/core#13260) is a duplicate of these issues:

• Empty - dummy sourcemap generation of components with setup directive #447
• Sourcemap points to wrong line for thrown error at <template> directive #500
• Template is not mapped in sourcemap on Vite applications vuejs/core#12682

and the fix you made on vuejs/core side (vuejs/core#12701) is more ideal.

[edison1105]

@sapphi-red
Thank you for your review, but they are not exactly the same.

• fix(compile-sfc): handle inline template source map in prod build vuejs/core#12701 fixes the production build map not including the template's sourcemap.
• The current PR fixes incorrect line numbers in the template's sourcemap when the script content is empty.

[sapphi-red]

My bad. You're right. Let's add a comment that this part also moves the mappings.