请帮个忙，看看哪里出错了

procedure TForm1.btn1Click(Sender: TObject);
var
  pts: array of TPoint;
  i,j,k: integer;
begin
  k := Random(10)+1;
  SetLength(pts,k);
  for j:=1 to 10 do
  begin
    for i:=1 to k do
    begin
      pts[i].X := Form1.Left + Image.Left + Random(Image.Width);
      pts[i].Y := Form1.Top + Image.Top + Random(Image.Height);
    end;
    Image.Canvas.Polygon(pts);
  end;
end;结果提示什么内存错误