Hi i got this error on process log while getting file attachments through web form

Error:

system.NullReferenceException: Object reference not set to an instance of an object.

   at Terrasoft.Core.Process.UsrUpdateLeadattachmentFromTempSectionMethodsWrapper.ScriptTask1Execute(ProcessExecutingContext context)

   at Terrasoft.Core.Process.ProcessFlowElement.Execute(ProcessExecutingContext context)

code in business process:

var leadtempfileid = Get("LeadTempFileId");

var leadid = Get("LeadId");

//to get Type column value for  Attachment table

var fileCode = "File";

var selFileType = new Select(UserConnection)

                  .Column("Id")

                .From("FileType")

                .Where("Code").IsEqual(Column.Parameter(fileCode))

                 as Select;

var typeId = selFileType.ExecuteScalar();

            

//to get data from Temp Lead attachment where filetypeId equals leadtempfileid 

var attachmentId = Guid.NewGuid();

var selTempAttachment = new Select(UserConnection)

                            .Column("Name")

                            .Column("Data")

                            .Column("UsrTempLeadId")

                          .From("UsrTempLeadFile")

                          .Where("Id").IsEqual(Column.Parameter(leadtempfileid))

                             as Select;

Guid UsrTempleadId = Guid.Empty;

byte[] fileContents = null;

string fileName = null;

using (DBExecutor dbExecutor = UserConnection.EnsureDBConnection())

{

    using (IDataReader dataReader = selTempAttachment.ExecuteReader(dbExecutor))

    {

        while (dataReader.Read())

        {

            fileContents = dataReader.GetColumnValue("Data");

            fileName = dataReader.GetColumnValue("Name");

            UsrTempleadId = dataReader.GetColumnValue("UsrTempLeadId");

            break;

        }

    }

}  

//to insert data into Lead attachment

using (DBExecutor dbExecutor = UserConnection.EnsureDBConnection())

            {

              dbExecutor.StartTransaction();

              var insLeadFile = new Insert(UserConnection)

                          .Into("FileLead")

                        .Set("Id", Column.Parameter(attachmentId))

                        .Set("LeadId", Column.Parameter(leadid))

                        .Set("TypeId", Column.Parameter(typeId))

                        .Set("Data", Column.Parameter(fileContents))

                        .Set("Size", Column.Parameter(fileContents.Length))

                        .Set("Name", Column.Parameter(fileName)).Execute();

               dbExecutor.CommitTransaction();

            }

            

Set("UsrTempLeadId",UsrTempleadId);

return true;

Can anyone help on this please,

Regards,

praveen