fix: fix broadcasting from a parent namespace (#5009)

Following [1], emitting from a dynamic namespace to a room would throw
this error:

> node_modules/socket.io/dist/parent-namespace.js:88
>         this.children.forEach((nsp) => {
>                       ^
> 
> TypeError: Cannot read properties of undefined (reading 'forEach')
>     at ParentBroadcastAdapter.broadcast (node_modules/socket.io/dist/parent-namespace.js:88:23)
>    at BroadcastOperator.emit (node_modules/socket.io/dist/broadcast-operator.js:169:26)
>    at Socket.<anonymous> (server.js:60:33)
>    at Socket.emit (node:events:520:28)
>    at Socket.emitReserved (node_modules/socket.io/dist/typed-events.js:56:22)
>    at Socket._onclose (node_modules/socket.io/dist/socket.js:547:14)
>    at Client.onclose (node_modules/socket.io/dist/client.js:247:20)
>    at Socket.emit (node:events:532:35)
>    at Socket.onClose (node_modules/engine.io/build/socket.js:304:18)
>    at Object.onceWrapper (node:events:639:28)

Previous output code:

```js
class ParentNamespace extends namespace_1.Namespace {
    constructor(server) {
        super(server, "/_" + ParentNamespace.count++);
        this.children = new Set();
    }
    _initAdapter() {
        this.adapter = new ParentBroadcastAdapter(this, this.children);
    }
}
```

Here, `super()` calls `Namespace._initAdapter()`, but `this.children`
is not defined yet, hence the problem.

[1]: b9ce6a2

Related: #4985

lib/parent-namespace.ts

@@ -48,7 +48,7 @@ export class ParentNamespace<
    * @private
    */
   _initAdapter(): void {
-    this.adapter = new ParentBroadcastAdapter(this, this.children);
+    this.adapter = new ParentBroadcastAdapter(this);
   }
 
   public emit<Ev extends EventNamesWithoutAck<EmitEvents>>(
@@ -113,12 +113,8 @@ export class ParentNamespace<
  * @private file
  */
 class ParentBroadcastAdapter extends Adapter {
-  constructor(parentNsp: any, private readonly children: Set<Namespace>) {
-    super(parentNsp);
-  }
-
   broadcast(packet: any, opts: BroadcastOptions) {
-    this.children.forEach((nsp) => {
+    this.nsp.children.forEach((nsp) => {
       nsp.adapter.broadcast(packet, opts);
     });
   }

test/namespaces.ts

@@ -525,6 +525,37 @@ describe("namespaces", () => {
       });
     });
 
+    it("should allow connections to dynamic namespaces with a regex and emit in a room", (done) => {
+      const io = new Server(0);
+      const socket = createClient(io, "/dynamic-101");
+      const partialDone = createPartialDone(4, successFn(done, io, socket));
+
+      let dynamicNsp = io
+        .of(/^\/dynamic-\d+$/)
+        .on("connect", (socket) => {
+          expect(socket.nsp.name).to.be("/dynamic-101");
+          socket.join("some-room");
+          dynamicNsp.to("some-room").emit("hello", 4, "3", { 2: "1" });
+          partialDone();
+        })
+        .use((socket, next) => {
+          next();
+          partialDone();
+        });
+      socket.on("connect_error", (err) => {
+        expect().fail();
+      });
+      socket.on("connect", () => {
+        partialDone();
+      });
+      socket.on("hello", (a, b, c) => {
+        expect(a).to.eql(4);
+        expect(b).to.eql("3");
+        expect(c).to.eql({ 2: "1" });
+        partialDone();
+      });
+    });
+
     it("should allow connections to dynamic namespaces with a function", (done) => {
       const io = new Server(0);
       const socket = createClient(io, "/dynamic-101");