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
if (ctrl != null) {
				if (ctrl.getParent() != ctf)
					ctrl.setParent(ctf);
				cti.setControl(ctrl);
			}
			
			
			String cssClassName = (String) ctf
					.getData("org.eclipse.e4.ui.css.CssClassName"); 
			stylingEngine.setClassname(cti, cssClassName);
		}
		
		hookTabControllerLogic(stack, part, cti);
		
		if (stack.getSelectedElement() == null)
			stack.setSelectedElement(part);
		if (stack.getSelectedElement() != null) {
			CTabItem selCTI = findItemForPart(stack, stack.getSelectedElement());
			if (selCTI != null && selCTI != ctf.getSelection())
				ctf.setSelection(selCTI);
		}
	}
	private int calcIndexFor(MElementContainer<MUIElement> stack,
			final MUIElement part) {
		int index = 0;
		
		for (MUIElement mPart : stack.getChildren()) {
			if (mPart == part)
				return index;
			if (mPart.isToBeRendered())