error message (Object reference not set to an instance of an object.)

protected void btnremove_Click(object sender, EventArgs e)
   {

      *** if (cat.removeCategory(Grid.SelectedRow.Cells[1].Text))
           lblmsg.Text = "category deleted successfully";
       else
           lblmsg.Text = "category not deleted , may have products";

       Grid.DataBind();
   //>>>>>>>>>>>>>>>>>>>>>>>>>>>>> and run the program flowing the step into:

  public bool removeCategory(string Catno)
    {
//?????????? look here?
        this.catno =Catno;
       return delete();
    }
//>>>>>>>> and then : this is method in a class :-  
 public bool delete()
    {
        return loadProperties2list("d"); //
    }

//>>>>>>>  the flowing and above is methods in class i called db:-
protected override bool loadProperties2list(string typeOfOperation)
    {
        SortedList sl = new SortedList();
        sl.Add("@check", typeOfOperation);
        sl.Add("@catno", catno);  ????????????? look here catno is null in  the table in database  but i can,t change it to not checked in allow null 
        sl.Add("@catname", catname);
        sl.Add("@description", description);
        procedureName = "manageCategory";
        if (dbVar.runProcedure(procedureName, sl) == 1)
            return true;
        else
            return false;
    }


//>>>>>>>>>>> and then in  step into :
public int runProcedure(string procedureName,SortedList paraVal)
    {
 initialize(CommandType.StoredProcedure, procedureName);
           
        for (int x = 0; x < paraVal.Count; x++)
            
            
            cmd.Parameters.AddWithValue(paraVal.GetKey(x).ToString(), paraVal.GetByIndex(x).ToString());   ////?????????? here the error message i show

        return  runUpdate();
}


//>>>>>>>>  in over it called:------
private void initialize(CommandType CT,string DBcall)
    {
          conn = new SqlConnection();
         cmd = new SqlCommand();


        
        conn.ConnectionString = ConfigurationManager.ConnectionStrings[1].ToString();
        cmd.Connection = conn;
        cmd.CommandType =CT ;
        cmd.CommandText = DBcall;
        conn.Open(); 
    }




//>>>>>>>>>>>>>>>>>>and here i find the error message (Object reference not set to an instance of an object.)


 cmd.Parameters.AddWithValue(paraVal.GetKey(x).ToString(), paraVal.GetByIndex(x).ToString());

//>>>>>>>>>>>> in above