site: fix 404 page by upgrading SvelteKit and avoiding null reference (#9337)

Author: benmccann

pnpm-lock.yaml

@@ -29,7 +29,7 @@
   "devDependencies": {
     "@resvg/resvg-js": "^2.4.1",
     "@sveltejs/adapter-vercel": "^3.0.3",
-    "@sveltejs/kit": "^1.24.1",
+    "@sveltejs/kit": "^1.26.0",
     "@sveltejs/site-kit": "6.0.0-next.50",
     "@sveltejs/vite-plugin-svelte": "^2.4.6",
     "@types/cookie": "^0.5.2",

sites/svelte.dev/package.json

@@ -24,7 +24,7 @@
 </script>
 
 <svelte:head>
-	{#if !$page.route.id.startsWith('/blog/')}
+	{#if !$page.route.id?.startsWith('/blog/')}
 		<meta name="twitter:card" content="summary" />
 		<meta name="twitter:image" content="https://svelte.dev/images/twitter-thumbnail.jpg" />
 		<meta name="og:image" content="https://svelte.dev/images/twitter-thumbnail.jpg" />