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
return null;
	}
	
	/**
	 * A compilation unit or class was expanded, expand
	 * the main type.  
	 */
	void expandMainType(Object element) {
		try {
			IType type= null;
			if (element instanceof ICompilationUnit) {
				ICompilationUnit cu= (ICompilationUnit)element;
				IType[] types= cu.getTypes();
				if (types.length > 0)
					type= types[0];
			}
			else if (element instanceof IClassFile) {
				IClassFile cf= (IClassFile)element;
				type= cf.getType();
			}			
			if (type != null) {
				final IType type2= type;
				Control ctrl= fViewer.getControl();
				if (ctrl != null && !ctrl.isDisposed()) {
					ctrl.getDisplay().asyncExec(new Runnable() {
						public void run() {
							Control ctrl2= fViewer.getControl();
							if (ctrl2 != null && !ctrl2.isDisposed()) 
								fViewer.expandToLevel(type2, 1);