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
super.handleInvalidSelection(invalidSelection, newSelection);
		}
		
		/**
		 * {@inheritDoc}
		 */
		protected Object[] addAditionalProblemParents(Object[] elements) {
			if (showWorkingSets()) {
				return fWorkingSetModel.addWorkingSets(elements);
			}
			return elements;
		}
		
		
		
		protected Object[] getSortedChildren(Object parent) {
			IParentAwareSorter sorter= getSorter() instanceof IParentAwareSorter 
				? (IParentAwareSorter)getSorter()
				: null;
			if (sorter != null)
				sorter.setParent(parent);
			try {
				return super.getSortedChildren(parent);
			} finally {
				if (sorter != null)
					sorter.setParent(null);
			}
		}