Error C#: Object Reference Not Set To an Instance Object?

Question

I create code for retrieve data from mysql (string and longblob), but i can't see the errors in my code. 

 

can you help me to fix this? I am using mysql (longblob) and retrieve image to picturebox. 

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Data.Odbc;
using System.IO;

namespace csharp_report
{
    public partial class frmMain : Form
    {
        public frmMain()
        {
            InitializeComponent();
        }

        OdbcConnection CONN;
        OdbcCommand CMD;
        DataSet DS;
        OdbcDataAdapter DA;
        OdbcDataReader DR;
        String LokasiData;

        public void Koneksi()
        {
            LokasiData = "Driver={MySQL ODBC 5.3 ANSI Driver};database=visualbasic_report;server=localhost;uid=root;pwd=";
            CONN = new OdbcConnection(LokasiData);
            if (CONN.State == ConnectionState.Closed)
            {
                CONN.Open();
            }
        }

        public void TampilGrid()
        {
            Koneksi();
            OdbcDataAdapter DA = new OdbcDataAdapter("select * from report", CONN);
            DataSet DS = new DataSet();
            DA.Fill(DS, "report");
            DataGridView1.DataSource = DS.Tables["report"];
            DataGridView1.ReadOnly = true;
        }

        public void TampilKembali()
        {
            try
            {
                CONN.Open();
                CMD.Connection = CONN;
                CMD.CommandType = CommandType.Text;
                CMD.CommandText = "Select * from report where kode='" + txtKode.Text + "'";
                DR = CMD.ExecuteReader();
                if (DR.HasRows)
                {
                    DR.Read();
                    txtNama.Text = DR["nama"].ToString();
                    txtAlamat.Text = DR["alamat"].ToString();
                    txtPekerjaan.Text = DR["pekerjaan"].ToString();
                    byte[] data = (byte[])DR["foto"];
                    MemoryStream ms = new MemoryStream(data);
                    ptbFoto.BackgroundImage = Image.FromStream(ms);
                    ptbFoto.BackgroundImageLayout = ImageLayout.Stretch;
                    DR.Close();
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
                //throw;
            }
        }

        private void DataGridView1_CellClick(object sender, DataGridViewCellEventArgs e)
        {
            DataGridViewRow row;
            row = DataGridView1.CurrentRow;
            txtKode.Text = row.Cells["kode"].Value.ToString();
            CONN.Close();
            TampilKembali();
        }

        private void frmMain_Load(object sender, EventArgs e)
        {
            TampilGrid();
        }

        private void btnReport_Click(object sender, EventArgs e)
        {
            String sTitle;
            sTitle = txtKode.Text;
            View frm = new View(sTitle);
            frm.Show();
        }
    }
}