fix: avoid errors when constructing the base path in certain edge cases

[CNSeniorious000]

In specific edge cases, new URL(..., location) may fail, such as when using an <iframe> with srcdoc set to the HTML of a SvelteKit page.

This pull request adds a condition to check if the protocol is about: or data: and handle the base URL resolution accordingly.

• Resolves Handle cases when location.protocol is about: or data: #13226

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🦋 Changeset detected

Latest commit: 8af8614

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

This PR includes changesets to release 1 package

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@sveltejs/kit	Patch

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[Rich-Harris]

preview: https://svelte-dev-git-preview-kit-13231-svelte.vercel.app/

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