System.NullReferenceException

Question

 

 

Hello guys
 
i got this error after i executed a bill update
here is the code underlined

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using System.Windows.Forms;
namespace NSPM_Sales_Invoice
{
static class Program
{
/// <summary>
/// The main entry point for the application.
/// </summary>
[STAThread]
static void Main()
{
Application.EnableVisualStyles();
Application.SetCompatibleTextRenderingDefault(false);
Application.Run(new Login());
}
}
}

please what could have gone wrong?