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
CTabItem item = findItemForPart(stack, uiElement);
				if (item == null) {
					return;
				}
				Boolean dirtyState = (Boolean) event
						.getProperty(UIEvents.EventTags.NEW_VALUE);
				String text = item.getText();
				boolean hasAsterisk = text.charAt(0) == '*';
				if (dirtyState.booleanValue()) {
					if (!hasAsterisk) {
						item.setText('*' + text);
					}
				} else if (hasAsterisk) {
					item.setText(text.substring(1));
				}
			}
		};
		eventBroker.subscribe(UIEvents.buildTopic(UIEvents.Dirtyable.TOPIC,
				UIEvents.Dirtyable.DIRTY), dirtyUpdater);
	}
	@PreDestroy
	public void contextDisposed() {
		super.contextDisposed(eventBroker);
		eventBroker.unsubscribe(itemUpdater);
		eventBroker.unsubscribe(dirtyUpdater);
	}
	private String getLabel(MUILabel itemPart, String newName) {
		if (newName == null) {
			newName = ""; 
		}