remove engine’s listener before assign new instance

Source/SocketEngine.swift

@@ -243,6 +243,11 @@ public final class SocketEngine : NSObject, URLSessionDelegate, SocketEnginePoll
     }
 
     private func createWebsocketAndConnect() {
+        
+        if let oldWs = ws {
+            oldWs.delegate = nil
+        }
+        
         ws = WebSocket(url: urlWebSocketWithSid as URL)
 
         if cookies != nil {

Source/SocketIOClient.swift

@@ -120,6 +120,10 @@ public final class SocketIOClient : NSObject, SocketEngineClient, SocketParsable
     private func addEngine() -> SocketEngineSpec {
         DefaultSocketLogger.Logger.log("Adding engine", type: logType, args: "")
 
+        if let oldEngine = engine {
+            oldEngine.client = nil
+        }
+        
         engine = SocketEngine(client: self, url: socketURL, config: config)
 
         return engine!