fix: prefer the default error page when failing to decode the URL pathname

[teemingc]

Previously, if a URL pathname could not be decoded, you'd get a text response. This PR makes it so that it renders the default error page instead which is a lot prettier for users. This only affects built apps because the Vite dev server intercepts malformed URIs

---

Please don't delete this checklist! Before submitting the PR, please make sure you do the following:

• It's really useful if your PR references an issue where it is discussed ahead of time. In many cases, features are absent for a reason. For large changes, please create an RFC: https://github.com/sveltejs/rfcs
• This message body should clearly illustrate what problems it solves.
• Ideally, include a test that fails without this PR but passes with it.

Tests

• Run the tests with pnpm test and lint the project with pnpm lint and pnpm check

Changesets

• If your PR makes a change that should be noted in one or more packages' changelogs, generate a changeset by running pnpm changeset and following the prompts. Changesets that add features should be minor and those that fix bugs should be patch. Please prefix changeset messages with feat:, fix:, or chore:.

Edits

• Please ensure that 'Allow edits from maintainers' is checked. PRs without this option may be closed.

[changeset-bot]

🦋 Changeset detected

Latest commit: 3bdd4ad

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

This PR includes changesets to release 1 package

Name	Type
@sveltejs/kit	Patch

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[svelte-docs-bot]

Preview: https://svelte-dev-git-preview-kit-15744-svelte.vercel.app/

[dummdidumm]

While this works, can we somehow rework this so that it returns a proper thing directly, instead of having to set the path to null and then hundreds of lines of code later return an error response?

[teemingc]

While this works, can we somehow rework this so that it returns a proper thing directly, instead of having to set the path to null and then hundreds of lines of code later return an error response?

Do you mean directly calling respond_with_error when we fail to decode? I tried that but the issue is I don't think we can get the transformPageChunk, filterSerializedResponseHeaders, preload resolve args until the actual resolve call.