Bug 299438 [CommonNavigator] CNF viewer state non properly reset when NCEs are activated or deactivated
The map of the objects to the NCEs should be reset whenever the NCEs associated with the viewer to change to avoid having stale label information. This has shown up when looking at the CNF tests that change the viewer.
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/StructuredViewer.java
* </p>
	 * @param widget
     *            the widget
	 * @param element
     *            the element
	 */
	protected final void refreshItem(Widget widget, Object element) {
		SafeRunnable.run(new UpdateItemSafeRunnable(widget, element, true));
	}
	/**
	 * Removes the given open listener from this viewer. Has no affect if an
	 * identical listener is not registered.
	 * 
	 * @param listener
	 *            an open listener
	 */
	public void removeOpenListener(IOpenListener listener) {
		openListeners.remove(listener);
	}
	/*
	 * (non-Javadoc) Method declared on IPostSelectionProvider.
	 */
	public void removePostSelectionChangedListener(ISelectionChangedListener listener) {
		postSelectionChangedListeners.remove(listener);
	}
	/**
	 * Removes the given double-click listener from this viewer. Has no affect
	 * if an identical listener is not registered.
	 * 
	 * @param listener