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).
tests/org.eclipse.e4.ui.tests/src/org/eclipse/e4/ui/tests/workbench/PartRenderingEngineTests.java
window.getChildren().add(part);
		window.setSelectedElement(part);
		application.setContext(appContext);
		appContext.set(MApplication.class.getName(), application);
		wb = new E4Workbench(application, appContext);
		wb.createAndRunUI(window);
		IPresentationEngine engine = appContext.get(IPresentationEngine.class);
		engine.removeGui(part);
		assertNull(part.getWidget());
		engine.createGui(part, null, window.getContext());
		engine.removeGui(part);
	}
	public void testBug331795_1() {
		MApplication application = ApplicationFactoryImpl.eINSTANCE
				.createApplication();
		MWindow window = BasicFactoryImpl.eINSTANCE.createWindow();
		application.getChildren().add(window);
		application.setSelectedElement(window);
		MPart part = BasicFactoryImpl.eINSTANCE.createPart();
		part.setContributionURI("platform:/plugin/org.eclipse.e4.ui.tests/org.eclipse.e4.ui.tests.workbench.SampleView");
		window.getChildren().add(part);
		window.setSelectedElement(part);
		application.setContext(appContext);
		appContext.set(MApplication.class.getName(), application);
		wb = new E4Workbench(application, appContext);
		wb.createAndRunUI(window);
		assertNotNull(part.getObject());
		assertNotNull(part.getContext());
		SampleView view = (SampleView) part.getObject();
		view.errorOnWidgetDisposal = true;