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>
	 * <p>
	 * The default implementation of this method tries first to find the widget
	 * for the given element assuming that it is the viewer's input; this is
	 * done by calling <code>doFindInputItem</code>. If it is not found
	 * there, the widgets are looked up in the internal element map provided
	 * that this feature has been enabled. If the element map is disabled, the
	 * widget is found via <code>doFindItem</code>.
	 * </p>
	 * 
	 * @param element
	 *            the element
	 * @return the corresponding widgets
	 * 
	 * @since 3.2
	 */
	protected final Widget[] findItems(Object element) {
		Widget result = doFindInputItem(element);
		if (result != null) {
			return new Widget[] { result };
		}
		
		if (usingElementMap()) {
			Object widgetOrWidgets = elementMap.get(element);
			if (widgetOrWidgets==null) {
				return NO_WIDGETS;
			} else if (widgetOrWidgets instanceof Widget) {
				return new Widget[] {(Widget) widgetOrWidgets};
			} else {
				return (Widget[])widgetOrWidgets;