From cc36b8bd01be453651829b41b0f6b407260ff137 Mon Sep 17 00:00:00 2001
From: Oceania2018 <haiping008@gmail.com>
Date: Tue, 19 Jun 2018 07:25:19 -0500
Subject: [PATCH] fix resposne message parameter

---
 BotSharp.Core/Engines/RequestExtension.cs | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/BotSharp.Core/Engines/RequestExtension.cs b/BotSharp.Core/Engines/RequestExtension.cs
index e7bfcc68..b271f9ea 100644
--- a/BotSharp.Core/Engines/RequestExtension.cs
+++ b/BotSharp.Core/Engines/RequestExtension.cs
@@ -228,7 +228,11 @@ namespace BotSharp.Core.Engines
             var reg = new Regex(@"\$\w+");
 
             reg.Matches(text).ToList().ForEach(token => {
-                text = text.Replace(token.Value, parameters.FirstOrDefault(x => x.Name == token.Value.Substring(1))?.Value.ToString());
+                var parameter = parameters.FirstOrDefault(x => x.Name == token.Value.Substring(1));
+                if(parameter != null)
+                {
+                    text = text.Replace(token.Value, parameter?.Value?.ToString());
+                }
             });
 
             return text;