Bug 319004 CCE caused by PartRenderingEngine assuming a parent eContainer() is an MElementContainer
An MMenu's container could be an MPart, which leads to a CCE in createGui(MUIElement).
bundles/org.eclipse.e4.ui.workbench.swt/src/org/eclipse/e4/ui/internal/workbench/swt/PartRenderingEngine.java
if (renderer != null)
					renderer.hideChild(changedElement, removed);
			}
		}
	};
	private EventHandler windowsHandler = new EventHandler() {
		public void handleEvent(Event event) {
			childrenHandler.handleEvent(event);
		}
	};
	private IEclipseContext appContext;
	protected Shell testShell;
	protected MApplication theApp;
	@Inject
	@Optional
	protected IEventBroker eventBroker;
	@Inject
	EModelService modelService;
	@Inject
	protected Logger logger;
	private Shell limbo;
	private List<MUIElement> renderedElements = new ArrayList<MUIElement>();
	private MUIElement removeRoot = null;
	@Inject
	public PartRenderingEngine(
			@Named(E4Workbench.RENDERER_FACTORY_URI) @Optional String factoryUrl) {
		if (factoryUrl == null) {
			factoryUrl = defaultFactoryUrl;
		}
		this.factoryUrl = factoryUrl;