Bug 317803 [CommonNavigator] NPE in WorkingSetsContentProvider
bundles/org.eclipse.ui.navigator.resources/src/org/eclipse/ui/internal/navigator/workingsets/WorkingSetsContentProvider.java
*/
	public void init(ICommonContentExtensionSite aConfig) {
		NavigatorContentService cs = (NavigatorContentService) aConfig.getService();
		viewer = (CommonViewer) cs.getViewer();
		projectExplorer = viewer.getCommonNavigator();
		
		extensionStateModel = aConfig.getExtensionStateModel();
		extensionStateModel.addPropertyChangeListener(rootModeListener);
		updateRootMode();
		
	}
	/* (non-Javadoc)
	 * @see org.eclipse.ui.navigator.IMementoAware#restoreState(org.eclipse.ui.IMemento)
	 */
	public void restoreState(IMemento aMemento) {
		
	}
	/* (non-Javadoc)
	 * @see org.eclipse.ui.navigator.IMementoAware#saveState(org.eclipse.ui.IMemento)
	 */
	public void saveState(IMemento aMemento) {
		
	}
	public Object[] getChildren(Object parentElement) {
		if (parentElement instanceof IWorkingSet) {
			IWorkingSet workingSet = (IWorkingSet) parentElement;
			if (workingSet.isAggregateWorkingSet()) {
				switch (projectExplorer.getRootMode()) {
					case ProjectExplorer.WORKING_SETS :
						return ((IAggregateWorkingSet) workingSet).getComponents();