Bug 321755 EPS adds a part without considering its placeholder if no target container or part stacks could be found
The summary probably makes no sense. Will deliver a fix with a test in a bit.
tests/org.eclipse.e4.ui.tests/src/org/eclipse/e4/ui/tests/application/EPartServiceTest.java
partDescriptor.setAllowMultiple(multipleAllowed);
		partDescriptor.setElementId("partId");
		application.getDescriptors().add(partDescriptor);
		initialize(applicationContext, application);
		getEngine().createGui(window);
		EPartService partService = (EPartService) window.getContext().get(
				EPartService.class.getName());
		MPart createdPart = partService.createPart("partId");
		MPart shownPart = partService.showPart(createdPart, partState);
		assertNotNull(shownPart);
		assertEquals(createdPart, shownPart);
	}
	public void testShowPart_Part_MultipleNonexistent_TrueACTIVATE() {
		testShowPart_Part_MultipleNonexistent(true, PartState.ACTIVATE);
	}
	public void testShowPart_Part_MultipleNonexistent_FalseACTIVATE() {
		testShowPart_Part_MultipleNonexistent(false, PartState.ACTIVATE);
	}
	public void testShowPart_Part_MultipleNonexistent_TrueVISIBLE() {
		testShowPart_Part_MultipleNonexistent(true, PartState.VISIBLE);
	}
	public void testShowPart_Part_MultipleNonexistent_FalseVISIBLE() {
		testShowPart_Part_MultipleNonexistent(false, PartState.VISIBLE);
	}
	public void testShowPart_Part_MultipleNonexistent_TrueCREATE() {
		testShowPart_Part_MultipleNonexistent(true, PartState.CREATE);
	}
	public void testShowPart_Part_MultipleNonexistent_FalseCREATE() {
		testShowPart_Part_MultipleNonexistent(false, PartState.CREATE);
	}