Fehler mit TreeView

[gerritlober]

Hi,
kann mir jemand sagen, wo hier der Fehler liegt?

Delphi-Quellcode:

procedure TMainWindow.FormShow(Sender: TObject);
var f: Textfile;
    text: String;
    Node: TTreeNode;
begin
  AssignFile(f, 'Theme.dat');
  if not DirectoryExists('Data') then MkDir('Data');
  if FileExists('Theme.dat') then Reset(f)
  else Rewrite(f);
  while not EOF(f) do begin
    Readln(f, text);
    trim(text);
    Node.Text := text;
    if tvChoice.Items.Count = 0 then
      tvChoice.Items.AddFirst(Node, text)
    else
      tvChoice.Items.Add(Node, text);
  end;
  CloseFile(f);
end;