code: public void unregisterMapAddon(MapAddon addon) {
  		if (addon != null && addons.containsKey(addon.getId())) {
  			addons.remove(addon.getId());
  			graphics.getVectorContext().deleteGroup(addon);
  			addon.onRemove();
  		}
  	}
docs: Remove a registered map add-on from the map. Map add-ons are fixed position entities on a map with possibly
  additional functionality. Examples are the scale bar, and navigation buttons.
  
  @param addon
  The add-on to be removed from the map. If it can't be found, nothing happens.