修复了全局节点连接异常异常。

Library/FlowNode/FlowResult.cs

@@ -3,6 +3,7 @@ using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Reactive;
+using System.Runtime.InteropServices;
 using System.Text;
 using System.Threading.Tasks;
 
@@ -23,7 +24,7 @@ namespace Serein.Library
     /// <summary>
     /// 流程返回值的包装
     /// </summary>
-    public class FlowResult
+    public sealed class FlowResult
     {
         /// <summary>
         /// 实例化返回值