public void closeEmptySessions() {
    JInternalFrame[] frames = desktopPane.getAllFramesInLayer(0);

    for (JInternalFrame frame : frames) {
      Object o = frame.getContentPane().getComponents()[0];

      if (o instanceof SessionEditor) {
        SessionEditor sessionEditor = (SessionEditor) o;
        SessionEditorWorkbench workbench = sessionEditor.getSessionWorkbench();
        Graph graph = workbench.getGraph();
        if (graph.getNumNodes() == 0) {
          frame.dispose();
        }
      }
    }
  }