I should inform that by setting insertIfEmpty property of salesLine datasource to false value, I remove the empty line and because there is no empty line the issue will not raised.
[FormDataSourceEventHandler(formDataSourceStr(ReturnTable, SalesLine), FormDataSourceEventType::Initialized)]
public static void SalesLine_OnInitialized(FormDataSource sender, FormDataSourceEventArgs e)
{
sender.insertIfEmpty(false);
}