public void propertyChange(PropertyChangeEvent event) {
   if (activeEditor == null) {
     return;
   }
   if (event.getSource() == undoAction) {
     if (event.getProperty().equals("chosen")) {
       activeEditor.undo();
     }
   } else if (event.getSource() == redoAction) {
     if (event.getProperty().equals("chosen")) {
       activeEditor.redo();
     }
   }
 }