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
}
		};
		ctf.addDisposeListener(new DisposeListener() {
			public void widgetDisposed(DisposeEvent e) {
				updateActiveTab.participating = false;
				folderContext.set(FOLDER_DISPOSED, Boolean.TRUE);
			}
		});
		folderContext.runAndTrack(updateActiveTab, null);
		return newWidget;
	}
	public void postProcess(MUIElement element) {
		super.postProcess(element);
		if (!(element instanceof MElementContainer<?>))
			return;
		MElementContainer<MUIElement> container = (MElementContainer<MUIElement>) element;
		CTabFolder ctf = (CTabFolder) element.getWidget();
		MPart selPart = ((MPartStack) element).getSelectedElement();
		if (selPart == null)
			return;
		
		CTabItem selItem = findItemForPart(container, selPart);
		if (selItem != null) {
			if (selPart.getWidget() == null) {
				IPresentationEngine renderer = (IPresentationEngine) getContext(
						selPart).get(IPresentationEngine.class.getName());
				renderer.createGui(selPart);
			}
			ctf.setSelection(selItem);
			showTab(container, selPart);