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
MPerspectiveStack perspectiveStack = AdvancedFactoryImpl.eINSTANCE
				.createPerspectiveStack();
		window.getChildren().add(perspectiveStack);
		window.setSelectedElement(perspectiveStack);
		MPerspective perspectiveA = AdvancedFactoryImpl.eINSTANCE
				.createPerspective();
		perspectiveA.setElementId("perspectiveA"); 
		perspectiveStack.getChildren().add(perspectiveA);
		perspectiveStack.setSelectedElement(perspectiveA);
		MPlaceholder placeholderA = AdvancedFactoryImpl.eINSTANCE
				.createPlaceholder();
		placeholderA.setRef(part);
		part.setCurSharedRef(placeholderA);
		perspectiveA.getChildren().add(placeholderA);
		perspectiveA.setSelectedElement(placeholderA);
		MPerspective perspectiveB = AdvancedFactoryImpl.eINSTANCE
				.createPerspective();
		perspectiveB.setElementId("perspectiveB"); 
		perspectiveStack.getChildren().add(perspectiveB);
		MPlaceholder placeholderB = AdvancedFactoryImpl.eINSTANCE
				.createPlaceholder();
		placeholderB.setRef(part);
		perspectiveB.getChildren().add(placeholderB);
		perspectiveB.setSelectedElement(placeholderB);
		application.setContext(appContext);
		appContext.set(MApplication.class.getName(), application);
		wb = new E4Workbench(application, appContext);
		wb.createAndRunUI(window);
		SampleView view = (SampleView) part.getObject();
		assertFalse(view.isDestroyed());