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>
	 * This method is internal to the framework; subclassers should not call
	 * this method.
	 * </p>
	 */
	protected void unmapAllElements() {
		if (elementMap != null) {
			elementMap = newHashtable(CustomHashtable.DEFAULT_CAPACITY);
		}
	}
	/**
	 * Removes the given element from the internal element to widget map. Does
	 * nothing if mapping is disabled. If mapping is enabled, the given element
	 * must be present.
	 * <p>
	 * This method is internal to the framework; subclassers should not call
	 * this method.
	 * </p>
	 * 
	 * @param element
	 *            the element
	 */
	protected void unmapElement(Object element) {
		if (elementMap != null) {
			elementMap.remove(element);
		}
	}
	/**
	 * Removes the given association from the internal element to widget map.
	 * Does nothing if mapping is disabled, or if the given element does not map