Bug 328296 DND of markers views causes NPE in StackRenderer
bundles/org.eclipse.e4.ui.workbench.renderers.swt/src/org/eclipse/e4/ui/workbench/renderers/swt/StackRenderer.java
public MElementContainer<MUIElement> stackToActivate = null;
		public void run() {
			activationJob = null;
			if (stackToActivate != null
					&& stackToActivate.getSelectedElement() != null) {
				
				
				
				
				MWindow win = modelService
						.getTopLevelWindowFor(stackToActivate);
				MPerspective activePersp = modelService
						.getActivePerspective(win);
				MPerspective myPersp = modelService
						.getPerspectiveFor(stackToActivate);
				if (activePersp != null && myPersp != activePersp)
					return;
				MUIElement selElement = stackToActivate.getSelectedElement();
				if (!selElement.isToBeRendered())