[MM-58500] Turn off PostedAck when the connection is no longer registered (#27212)

* [MM-58500] Turn off PostedAck when the connection is no longer registered

* Expose active and just check for active instead

server/channels/app/web_broadcast_hooks.go

@@ -83,7 +83,7 @@ func usePostedAckHook(message *model.WebSocketEvent, postedUserId string, channe
 
 func (h *postedAckBroadcastHook) Process(msg *platform.HookedWebSocketEvent, webConn *platform.WebConn, args map[string]any) error {
 	// Don't ACK unless we say to explicitly
-	if !webConn.PostedAck {
+	if !(webConn.PostedAck && webConn.Active.Load()) {
 		return nil
 	}