Bug 81426 Package Explorer shows nothing after drill into working set, then show projects
I200412160800 - switch Package Explorer to working sets - context menu > Go Into a working set - Show > Projects -> view is empty -> view toolbar button 'Up to Working Sets' does not do anything
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/packageview/PackageExplorerPart.java
JavaPlugin.getDefault().getPreferenceStore().addPropertyChangeListener(this);
	
		
		MenuManager menuMgr= new MenuManager("#PopupMenu"); 
		menuMgr.setRemoveAllWhenShown(true);
		menuMgr.addMenuListener(this);
		fContextMenu= menuMgr.createContextMenu(fViewer.getTree());
		fViewer.getTree().setMenu(fContextMenu);
		
		
		IWorkbenchPartSite site= getSite();
		site.registerContextMenu(menuMgr, fViewer);
		site.setSelectionProvider(fViewer);
		site.getPage().addPartListener(fPartListener);
		
		if (fMemento != null) {
			restoreLinkingEnabled(fMemento);
		}
		
		makeActions(); 
		
		
		restoreFilterAndSorter();
		fViewer.setInput(findInputElement());
		initFrameActions();
		initKeyListener();
			
		fViewer.addPostSelectionChangedListener(fSelectionListener);
		
		fViewer.addDoubleClickListener(new IDoubleClickListener() {