[Fix] Separate it

Fix for issue #232

websocket-sharp/Net/EndPointListener.cs

@@ -243,6 +243,12 @@ namespace WebSocketSharp.Net
       Socket sock = null;
       try {
         sock = lsnr._socket.EndAccept (asyncResult);
+      }
+      catch (ObjectDisposedException) {
+        return;
+      }
+
+      try {
         lsnr._socket.BeginAccept (onAccept, lsnr);
       }
       catch {
@@ -252,6 +258,9 @@ namespace WebSocketSharp.Net
         return;
       }
 
+      if (sock == null)
+        return;
+
       processAccepted (sock, lsnr);
     }