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
if (parent != null) {
			IStructuredContentProvider cp = (IStructuredContentProvider) getContentProvider();
			if (cp != null) {
				result = cp.getElements(parent);
				assertElementsNotNull(result);
			}
		}
		return (result != null) ? result : new Object[0];
	}
	/**
	 * Returns the root element.
	 * <p>
	 * The default implementation of this framework method forwards to
	 * <code>getInput</code>. Override if the root element is different from
	 * the viewer's input element.
	 * </p>
	 * 
	 * @return the root element, or <code>null</code> if none
	 */
	protected Object getRoot() {
		return getInput();
	}
	/**
	 * The <code>StructuredViewer</code> implementation of this method returns
	 * the result as an <code>IStructuredSelection</code>.
	 * <p>
	 * Subclasses do not typically override this method, but implement
	 * <code>getSelectionFromWidget(List)</code> instead.
	 * <p>
	 * @return ISelection