Bug 329310 Part service does not autogenerate stacks if the last container is not one
bundles/org.eclipse.e4.ui.workbench/src/org/eclipse/e4/ui/internal/workbench/PartServiceImpl.java
getContainer().getChildren().add(stack);
			}
		} else {
			if (providedPart != localPart && !descriptor.isAllowMultiple()) {
				return localPart;
			}
			if (isInContainer(providedPart)) {
				return providedPart;
			}
			adjustPlaceholder(providedPart);
			String category = descriptor.getCategory();
			if (category == null) {
				addToLastContainer(null, providedPart);
			} else {
				List<MElementContainer> containers = modelService.findElements(getContainer(),
						null, MElementContainer.class, Collections.singletonList(category));
				if (containers.isEmpty()) {
					addToLastContainer(category, providedPart);
				} else {
					MElementContainer container = containers.get(0);
					MPlaceholder placeholder = providedPart.getCurSharedRef();
					if (placeholder == null) {
						container.getChildren().add(providedPart);
					} else {
						container.getChildren().add(placeholder);
					}
				}
			}
		}
		return providedPart;