结束会签时，不置空TopCountersignStepId

src/Hotline/FlowEngine/Workflows/Workflow.cs

@@ -641,7 +641,7 @@ public partial class Workflow
     public void EndCountersign()
     {
         IsInCountersign = false;
-        TopCountersignStepId = null;
+        //TopCountersignStepId = null;
     }
 
     /// <summary>