Bug 327964 EPartService's hidePart may fail when trying to hide a shared part that's in a shared container
The placeholder retrieval code in the EPartService implementation doesn't go far down deep enough and actually stops at the shared container level. This causes the placeholder of the shared part to not be found.
bundles/org.eclipse.e4.ui.workbench/src/org/eclipse/e4/ui/internal/workbench/PartServiceImpl.java
}
	private MElementContainer<?> getLastContainer() {
		MElementContainer<MUIElement> searchRoot = getContainer();
		List<MUIElement> children = searchRoot.getChildren();
		if (children.size() == 0) {
			MPartStack stack = BasicFactoryImpl.eINSTANCE.createPartStack();
			searchRoot.getChildren().add(stack);
			return stack;
		}
		MElementContainer<?> lastContainer = getLastContainer(searchRoot, children);
		if (lastContainer == null) {
			MPartStack stack = BasicFactoryImpl.eINSTANCE.createPartStack();
			searchRoot.getChildren().add(stack);
			return stack;
		}
		return lastContainer;
	}
	private MElementContainer<?> getLastContainer(MElementContainer<?> container, List<?> children) {
		if (children.isEmpty()) {
			return null;
		}
		for (int i = children.size() - 1; i > -1; i--) {
			Object muiElement = children.get(i);
			if (muiElement instanceof MElementContainer<?>) {
				MElementContainer<?> childContainer = (MElementContainer<?>) muiElement;
				MElementContainer<?> lastContainer = getLastContainer(childContainer,
						childContainer.getChildren());
				if (lastContainer != null) {
					return lastContainer;
				}