修正 Memo 設定為 ReadOnly 後, 無法有複製的功能

procedure TWindowManager.ShowContextMenu(const ItemsToShow: TContextMenuItems);
begin

  ..... 省略 ......

    PlatformAndroid.SynchronizeOnUIThread(
      procedure
      begin
        if FCopyButton <> nil then
          FContextButtonsLayout.addView(FCopyButton);
        if FCutButton <> nil then
          FContextButtonsLayout.addView(FCutButton);
        if FPasteButton <> nil then
          FContextButtonsLayout.addView(FPasteButton);
//  if TVirtualKeyboardState.Visible in VirtualKeyboardAndroid.VirtualKeyboardState then // 删除这一行
          DoShowContextMenu;
      end);
  end;
end;