[BlackMonsta]

не пойму почему выходит ошибка :

Код:

unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, ComCtrls, StdCtrls, OleCtrls, SHDocVw, Menus;

type
  TForm1 = class(TForm)
    Button1: TButton;
    Button2: TButton;
    Button3: TButton;
    PageControl1: TPageControl;
    WebBrowser1: TWebBrowser;
    PopupMenu1: TPopupMenu;
    procedure Button1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

TWebTabSheet = class (TTabSheet)
  private
    ppdisp: IDispatch;
    FBrowser: TWebBrowser;
  public
    property Browser: TWebBrowser read FBrowser;
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.Button1Click(Sender: TObject);
var
  ts: TWebTabSheet;
  popup: TPopupMenu;
begin
  ts:= TWebTabSheet.Create(PageControl1);
  ts.PageControl:= PageControl1;
  ts.Caption:= 'New Page';
  PageControl1.ActivePage:= ts;
  popup:= TPopupMenu.Create(Self);
  ts.PopupMenu:= (PageControl1.ActivePage as TWebTabSheet).PopupMenu;
end;

procedure TForm1.Button2Click(Sender: TObject);
var
PopupItm: TMenuItem;
begin
PopupItm:= TMenuItem.Create(nil);
PopupItm.Caption:= (PageControl1.ActivePage as TWebTabSheet).Caption;
(PageControl1.ActivePage as TWebTabSheet).PopupMenu.Items.Add(PopupItm);
end;

end.

Когда вызываю Button2 то выходит ошибка... не пойму почему