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
*            the selection, or <code>null</code> if none
	 */
	protected void updateSelection(ISelection selection) {
		SelectionChangedEvent event = new SelectionChangedEvent(this, selection);
		fireSelectionChanged(event);
	}
	/**
	 * Returns whether this structured viewer is configured to use an internal
	 * map to speed up the mapping between elements and SWT items.
	 * <p>
	 * The default implementation of this framework method checks whether the
	 * internal map has been initialized.
	 * </p>
	 * 
	 * @return <code>true</code> if the element map is enabled, and
	 *         <code>false</code> if disabled
	 */
	protected boolean usingElementMap() {
		return elementMap != null;
	}
	/* (non-Javadoc)
	 * @see org.eclipse.jface.viewers.ContentViewer#setLabelProvider(org.eclipse.jface.viewers.IBaseLabelProvider)
	 */
	public void setLabelProvider(IBaseLabelProvider labelProvider) {
		if (labelProvider instanceof IColorProvider || labelProvider instanceof IFontProvider) {
			colorAndFontCollector = new ColorAndFontCollectorWithProviders(labelProvider);
		} else {
			colorAndFontCollector = new ColorAndFontCollector();
		}
		super.setLabelProvider(labelProvider);