Tidy up worker

package.json

@@ -1,6 +1,6 @@
 {
   "name": "fflate",
-  "version": "0.6.7",
+  "version": "0.6.8",
   "description": "High performance (de)compression in an 8kB package",
   "main": "./lib/index.cjs",
   "module": "./esm/browser.js",

src/index.ts

@@ -1482,7 +1482,7 @@ export class AsyncGunzip {
    * Creates an asynchronous GUNZIP stream
    * @param cb The callback to call whenever data is deflated
    */
-  constructor(cb: AsyncFlateStreamHandler) {
+  constructor(cb?: AsyncFlateStreamHandler) {
     this.ondata = cb;
     astrmify([
       bInflt,

src/worker.ts

@@ -3,14 +3,13 @@ const ch2: Record<string, string> = {};
 let durl = (c: string) => URL.createObjectURL(new Blob([c], { type: 'text/javascript' }));
 
 try {
-  durl('')
+  URL.revokeObjectURL(durl(''));
 } catch(e) {
   durl = c => 'data:application/javascript;charset=UTF-8,' + encodeURI(c);
 }
 
 export default <T>(c: string, id: number, msg: unknown, transfer: ArrayBuffer[], cb: (err: Error, msg: T) => void) => {
-  const u = ch2[id] ||= durl(c);
-  const w = new Worker(u);
+  const w = new Worker(ch2[id] ||= durl(c));
   w.onerror = e => cb(e.error, null);
   w.onmessage = e => cb(null, e.data);
   w.postMessage(msg, transfer);