Bug 303549 [UI] Dragging the last element from a stack causes placeholders to appear
The check to 'pick' a new element to select isn't checking whether the 'toBeRendered' is true.
bundles/org.eclipse.e4.ui.workbench.renderers.swt/src/org/eclipse/e4/workbench/ui/renderers/swt/StackRenderer.java
private static final String FOLDER_DISPOSED = "folderDisposed"; 
	Image viewMenuImage;
	@Inject
	IStylingEngine stylingEngine;
	@Inject
	IEventBroker eventBroker;
	@Inject
	IPresentationEngine renderer;
	private EventHandler itemUpdater;
	private EventHandler dirtyUpdater;