Вылетает ошибка invalid class typecast

procedure TForm3.Button1Click(Sender: TObject);
var img: TImage;
     i,imageCount:integer;
begin
  imageCount:=-1;
  for i:=0 to ControlCount-1 do
    Begin
      if (Controls[i] is TImage) then
        inc(imageCount);
    End;
if imageCount=-1 then
  Begin
    img:=TImage.Create(Form3);
    img.Name:='Image1';
    img.Parent:=Form3;
    img.Left:=10;
    img.Top:=10;
    img.Width:=155;
    img.Height:=130;
    img.Picture.LoadFromFile(ExtractFilepath(Application.ExeName)+'\Shablons\111.jpg');
  End
else
  Begin
    img:=TImage.Create(Form3);
    img.Name:='Image'+IntToStr(imageCount+2);
    img.Parent:=Form3;
    img.Left:=(Controls[imageCount] as TImage).Left+(Controls[imageCount] as TImage).Width+10;
    img.Top:=10;
    img.Width:=155;
    img.Height:=130;
    img.Picture.LoadFromFile(ExtractFilepath(Application.ExeName)+'\Shablons\111.jpg');
  End;
end;

img.Left:=(Controls[imageCount] as TImage).Left+(Controls[imageCount] as TImage).Width+10;

TForm1=class
...
ImgList : TObjectList<TImage>;
end;

ImgList:=TObjectList<TImage>.Create(true);

FreeAndNil(ImgList);

Img:=TImage.Create(Self);
ImgList.Add(Img);

TForm1=class
...
ImgList : TObjectList;
end;
...
ImgList:=TObjectList.Create(true);
...
Img:=TImage.Create(Self);
ImgList.Add(Img);
...
Img := TImage(ImgList[i]);