Bug 336225 Trim bars do not get unrendered by the rendering engine when trimmed window is unrendered
The trim bars are "ignored" by the rendering engine as it does not perform an unrendering pass on them when the parent trimmed window is being unrendered.
tests/org.eclipse.e4.ui.tests/src/org/eclipse/e4/ui/tests/workbench/PartRenderingEngineTests.java
boolean causedException = false;
		try {
			stack.setSelectedElement(partA);
		} catch (IllegalArgumentException e) {
			causedException = true;
		}
		assertFalse("Exception should not have been thrown", causedException);
		
		causedException = false;
		try {
			stack.setSelectedElement(partC);
		} catch (IllegalArgumentException e) {
			causedException = true;
		}
		assertTrue("Exception should have been thrown", causedException);
	}
	public void testSelectedElementNullingTBR() {
		MApplication application = ApplicationFactoryImpl.eINSTANCE
				.createApplication();
		application.setContext(appContext);
		appContext.set(MApplication.class.getName(), application);
		MWindow window = BasicFactoryImpl.eINSTANCE.createWindow();
		application.getChildren().add(window);
		MPartSashContainer container = BasicFactoryImpl.eINSTANCE
				.createPartSashContainer();
		window.getChildren().add(container);
		MPart partA = BasicFactoryImpl.eINSTANCE.createPart();
		partA.setElementId("partA");
		partA.setContributionURI("platform:/plugin/org.eclipse.e4.ui.tests/org.eclipse.e4.ui.tests.workbench.SampleView");