added code

CRM.Visitors/ActionProviders/VisitorStageChangeAndUpDateContacts.cs

                 {
                     long installedAppId = 0;
                     var stageStatusName = "";
+                    var code = "";
                     var visitorIds = Convert.ToInt64(visitorInfo.Parameters["visitorid"]);
-                    var visitorType = Convert.ToInt64(visitorInfo.Parameters["visitortype"]);
-                    var code = visitorInfo.Parameters["code"].ToString();
+                    var visitorType = Convert.ToInt64(visitorInfo.Parameters["visitortype"]);                   
                     var visitordata = await visitorManager.GetVisitorByIdAsync(srequest, visitorIds);
                     if (visitordata.Result != null)
                     {
                         if (visitorType == 1)
                         {
                             stageStatusName = "CheckIn";
+                            code = visitorInfo.Parameters["code"].ToString();
                         }
                         else
                         {
                             stageStatusName = "Pre-Invite";
                             defaultPKValue = visitorIds;
+                            code = visitorInfo.Parameters["accesscode"].ToString();
                         }
                         mobileNumber = visitordata.Result.MobileNumber;
                         emailId = visitordata.Result.EmailId;