Special characters breaking the page (Important AF)

[xtance]

Describe the bug

This is dangerous! Especially if you output any user-submitted data on your page
This symbol is preventing json from parsing. https://pastebin.com/0iWwevN2
Coming from serverside to clientside it will break the page. (tested in chrome and waterfox)

(Just read the reproduction, I will try to explain it there)
I also created a repo for this https://github.com/xtance/sveltekit-problem

Reproduction

1. Create a page like this:
   +page.server.ts

/** @type {import('./$types').PageServerLoad} */
export async function load({  }) {
	let str = '�';
	return ({ str });
}

+page.svelte

<script>
	export let data;
</script>

<div>This page will only be rendered after F5</div>

2. Go to that page from another SvelteKit page <- this is important. You need to click on link pointing to that page.
   What you get is SyntaxError: Unexpected token � in JSON at position 74
   And then "500 Internal Error" instead of the page
   (If you refresh the page, or navigate straight to it instead of a href there s no such bug)

Some motherfucker used that as a nickname on my site now no one can visit his page + every page containing his username also broke.
Sure this sounds emotional but IMHO this is dangerous

Logs

SyntaxError: Unexpected token � in JSON at position 74`

System Info

System:
    OS: Windows 10 10.0.17763
    CPU: (4) x64 Intel(R) Pentium(R) CPU G4620 @ 3.70GHz
    Memory: 8.23 GB / 15.84 GB
  Binaries:
    Node: 18.12.0 - C:\Program Files\nodejs\node.EXE
    npm: 8.19.2 - C:\Program Files\nodejs\npm.CMD
  Browsers:
    Internet Explorer: 11.0.17763.771
  npmPackages:
    @sveltejs/adapter-auto: ^1.0.0 => 1.0.2
    @sveltejs/kit: ^1.0.0 => 1.3.3
    svelte: ^3.54.0 => 3.55.1
    vite: ^4.0.0 => 4.0.4

Severity

blocking all usage of SvelteKit

Additional Information

Please fix and thanks in advance <3