site: fix handling of non-existent blog posts (#2439)

site/src/routes/blog/[slug].json.js

@@ -16,5 +16,8 @@ export function get(req, res) {
 			'Cache-Control': `max-age=${5 * 60 * 1e3}` // 5 minutes
 		});
 		res.end(lookup.get(req.params.slug));
+	} else {
+		res.statusCode = 404;
+		res.end(JSON.stringify({ message: 'not found' }));
 	}
 }

site/src/routes/blog/[slug].svelte

@@ -1,7 +1,7 @@
 <script context="module">
 	export async function preload({ params }) {
-		const post = await this.fetch(`blog/${params.slug}.json`).then(r => r.json());
-		return { post };
+		const res = await this.fetch(`blog/${params.slug}.json`);
+		return res.ok ? { post: await res.json() } : this.error(404, 'Not found');
 	}
 </script>