fix: Ensure sourcemap `sourcesContent` exists before trying to consume

[rschristian]

Closes #926

Per the spec, sourcesContent is optional so we need to check for its existence before consuming.

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🦋 Changeset detected

Latest commit: 2c251f0ceeaaa802c73efb628122c93b21976565

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
wmr	Patch

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Size Change: 0 B

Total Size: 805 kB

ℹ️ View Unchanged

Filename	Size
examples/demo/dist/about/index.html	720 B
examples/demo/dist/alias-outside/index.html	697 B
examples/demo/dist/assets/Calendar.********.css	694 B
examples/demo/dist/assets/style.********.css	624 B
examples/demo/dist/chunks/alias-outside.********.js	139 B
examples/demo/dist/chunks/class-fields.********.js	211 B
examples/demo/dist/chunks/compat.********.js	16.9 kB
examples/demo/dist/chunks/hoofd.module.********.js	1.48 kB
examples/demo/dist/chunks/index.********.js	303 B
examples/demo/dist/chunks/json.********.js	238 B
examples/demo/dist/chunks/meta-tags.********.js	298 B
examples/demo/dist/chunks/prerender.********.js	294 B
examples/demo/dist/class-fields/index.html	709 B
examples/demo/dist/compat/index.html	1.56 kB
examples/demo/dist/env/index.html	786 B
examples/demo/dist/error/index.html	714 B
examples/demo/dist/files/index.html	743 B
examples/demo/dist/index.********.js	8.2 kB
examples/demo/dist/index.html	775 B
examples/demo/dist/json/index.html	720 B
examples/demo/dist/lazy-and-late/index.html	723 B
examples/demo/dist/meta-tags/index.html	789 B
packages/wmr/wmr.cjs	767 kB

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