Access Violation при OpenDialog->Execute()

#ifndef Unit1H
#define Unit1H
//---------------------------------------------------------------------------
#include <Classes.hpp>
#include <Controls.hpp>
#include <StdCtrls.hpp>
#include <Forms.hpp>
#include <Buttons.hpp>
//---------------------------------------------------------------------------
class TForm1 : public TForm
{
__published:    // IDE-managed Components
        TBitBtn *BitBtn1;
        void __fastcall BitBtn1Click(TObject *Sender);
        void __fastcall FormClose(TObject *Sender, TCloseAction &Action);
private:    // User declarations
TOpenDialog *OpenDialog;
public:     // User declarations
        __fastcall TForm1(TComponent* Owner);
};

void __fastcall TForm1::BitBtn1Click(TObject *Sender)
{
OpenDialog = new TOpenDialog(NULL);
if(OpenDialog->Execute()){
ShowMessage(OpenDialog->FileName);
}
}
//---------------------------------------------------------------------------

void __fastcall TForm1::FormClose(TObject *Sender, TCloseAction &Action)
{
delete OpenDialog;
Action = caFree;        
}