public final Workbench getWorkbench() {
    return workbench.get();
  }
The dialog's action, which is invoked whenever the dialog has been hidden in the scene graph.
An event will be fired whenever {@link #hide()} or
{@link Workbench#hideDialog(WorkbenchDialog)} has been called or the dialog has been closed by
clicking on its corresponding {@link GlassPane}.

@return the property to represent the event, which is invoked whenever the dialog has been
    hidden in the scene graph.
workbenchfx-core/src/main/java/com/dlsc/workbenchfx/view/controls/dialog/DialogControl.java