handle vendorId null

EVCB_OCPP.WSServer/Helper/DbExtention.cs

@@ -72,8 +72,8 @@ namespace EVCB_OCPP.WSServer.Helper
                 new SqlParameter("CreatedOn", SqlDbType.DateTime) { Value = createdOn },
                 new SqlParameter("ChargePointErrorCodeId", SqlDbType.Int) { Value = chargePointErrorCodeId },
                 new SqlParameter("ErrorInfo",SqlDbType.NVarChar, 50){ Value = errorInfo is null ? DBNull.Value : errorInfo },
-                new SqlParameter("VendorId", SqlDbType.NVarChar, 255){ Value = vendorId },
-                new SqlParameter("VendorErrorCode", SqlDbType.NVarChar, 100) {Value =vendorErrorCode },
+                new SqlParameter("VendorId", SqlDbType.NVarChar, 255){ Value = vendorId is null ? DBNull.Value : vendorId },
+                new SqlParameter("VendorErrorCode", SqlDbType.NVarChar, 100) {Value =vendorErrorCode is null ? DBNull.Value : vendorErrorCode},
             };
             sqlParameters.AddRange(parameter);
         }