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
List stable= new ArrayList(l);
				super.internalRefresh(element, updateLabels);
				for (Iterator iter= stable.iterator(); iter.hasNext();) {
					Widget item= (Widget)iter.next();
					super.internalRefresh(item, element, true, updateLabels);				
				}
			}
		}
		protected void internalUpdate(Widget item, Object element, String[] properties) {
			List l= (List)fAdditionalMappings.get(element);
			if (l == null) {
				super.internalUpdate(item, element, properties);
			} else {
				List stable= new ArrayList(l);
				super.internalUpdate(item, element, properties);
				for (Iterator iter= stable.iterator(); iter.hasNext();) {
					Widget additionalItem= (Widget)iter.next();
					super.internalUpdate(additionalItem, element, properties);
				}
			}
		}
		public ISelection getSelection() {
			IContentProvider cp= getContentProvider();
			if (!(cp instanceof IMultiElementTreeContentProvider)) {
				return super.getSelection();
			}
			Control control = getControl();
			if (control == null || control.isDisposed()) {
				return StructuredSelection.EMPTY;
			}