Form Fecha e depois não abri mais (FireMonkey)

unit uPrincipal;

interface

uses
  System.SysUtils, System.Types, System.UITypes, System.Classes,
  System.Variants,
  FMX.Types, FMX.Controls, FMX.Forms, FMX.Graphics, FMX.Dialogs, FMX.Menus,
  FMX.Layouts, FMX.Controls.Presentation, FMX.StdCtrls;

type
  Tfrm_Principal = class(TForm)
    ToolBar1: TToolBar;
    LayoutPrincipal: TLayout;
    Button1: TButton;
    procedure MenuDeslogarClick(Sender: TObject);
    procedure Button1Click(Sender: TObject);
  private

    FFormularioAtivo: TForm;
    procedure AbrirJanela(AClasseFormulario: TComponentClass);

    { Private declarations }
  public
    { Public declarations }
  end;

var
  frm_Principal: Tfrm_Principal;

implementation

{$R *.fmx}

uses uLF_Jogos;

procedure Tfrm_Principal.AbrirJanela(AClasseFormulario: TComponentClass);
var
  LayoutBase: TComponent;
begin
  if Assigned(FFormularioAtivo) then
  begin
    if FFormularioAtivo.ClassType = AClasseFormulario then
    begin
      Exit
    end
    else
    begin
      FFormularioAtivo.DisposeOf;
      FFormularioAtivo := nil;
    end;
  end;
  Application.CreateForm(AClasseFormulario, FFormularioAtivo);
  LayoutBase := FFormularioAtivo.FindComponent('Layout_Principal');
  if Assigned(LayoutBase) then
    LayoutPrincipal.AddObject(TLayout(LayoutBase));
end;

procedure Tfrm_Principal.Button1Click(Sender: TObject);
begin

  // FFormularioAtivo.DisposeOf;
  // FFormularioAtivo := nil;
  AbrirJanela(Tfrm_Resultados_LF);

end;

procedure Tfrm_Principal.MenuDeslogarClick(Sender: TObject);
begin
  Close;
end;

end.

procedure Tfrm_Resultados_LF.FormClose(Sender: TObject;
  var Action: TCloseAction);
begin


  action := TCloseAction.caFree;
  frm_Resultados_LF := nil;

end;