public void removeUnexistingEntries()
  {
    for (Iterator<CButton> it = setButtons.iterator(); it.hasNext();)
    {
      CButton cButton = it.next();
      for (Iterator<MediaElement> it1 = cButton.getMedias().iterator(); it1.hasNext();)
      {
        MediaElement mediaElement = it1.next();
        if (mediaElement.getVisible())
          if (!new File(mediaElement.getPath()).exists())
          {
            Prefs.getInstance().getPrefs().remove(getStringHashcode(mediaElement.getPath()));
            it1.remove();
          }
      }

      if (cButton.getMedias().isEmpty())
        it.remove();
    }
  }