Object reference not set to an instance of an object. !ISPOSTBACK

Hello,

I am getting the Object Reference message but I am confused because I did create an instance of the base class in the calling program " CheckProgramAccess CPA = new CheckProgramAccess()"

The error is being thrown within the .DLL at this statement:
"string TrackId = HttpContext.Current.Request.QueryString["track"].Substring(0,8) ;"

The Part 2 of the code is in a .dll which I am not allowed to change.  So my question is - two fold:
1). Why is this error happening since I did create an instance as demonstrated by CPA....and
2). How do I resolve this within my Part 1 code sniplet?

Thank you!

Part#1:
 protected void Page_Load(object sender, EventArgs e)
 
        {
        if (!IsPostBack)
            {
            CheckProgramAccess CPA = new CheckProgramAccess();
 
            if (!CPA.Authorized())
                {
                Response.Redirect("/asp/home.asp");
                }
            else
                {
 
                }
            }
=========
Part# 2:
 
public class CheckProgramAccess
	{
		public CheckProgramAccess()
		{
			//
			// TODO: Add constructor logic here
			//
		}
 
		public bool Authorized()
		{
			bool Authenticated = true;
			bool RtnCde = false ;
			string UpId = "" ;
			string TimeOut = "" ;
			string LogTime = "" ;
 
			try
			{
				string TrackId = HttpContext.Current.Request.QueryString["track"].Substring(0,8) ;
				string Program =  HttpContext.Current.Request.QueryString["program"].ToString() ;
	}
			catch(Exception ex)
			{
				string msg = ex.Message.ToString();
				Authenticated = false ;
			}
			return Authenticated;
		}

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