explicitly handle http 404 in cache build script

Author: p2r3

buildCache.js

@@ -3,7 +3,9 @@ import puppeteer from "puppeteer";
 const server = Bun.serve({
   async fetch (req) {
     const path = new URL(req.url).pathname.replace("/convert/", "") || "index.html";
-    return new Response(Bun.file(`${__dirname}/dist/${path}`));
+    const file = Bun.file(`${__dirname}/dist/${path}`);
+    if (!(await file.exists())) return new Response("Not Found", { status: 404 });
+    return new Response(file);
   },
   port: 8080
 });