Do not send unsubscribe messages to destroyed Providers (#4678).

src.ts/providers/provider-socket.ts

@@ -69,6 +69,7 @@ export class SocketSubscriber implements Subscriber {
 
     stop(): void {
         (<Promise<number>>(this.#filterId)).then((filterId) => {
+            if (this.#provider.destroyed) { return; }
             this.#provider.send("eth_unsubscribe", [ filterId ]);
         });
         this.#filterId = null;

src.ts/providers/subscriber-filterid.ts

@@ -118,6 +118,7 @@ export class FilterIdSubscriber implements Subscriber {
         if (filterIdPromise) {
             this.#filterIdPromise = null;
             filterIdPromise.then((filterId) => {
+                if (this.#provider.destroyed) { return; }
                 this.#provider.send("eth_uninstallFilter", [ filterId ]);
             });
         }