Bug 329930 Resetting a perspective while its active part is not defined in the perspective causes the perspective to not have an active part after the reset
1. Window > Show View > Console 2. Window > Reset Perspective... > OK 3. No parts are active.
bundles/org.eclipse.e4.ui.workbench/src/org/eclipse/e4/ui/internal/workbench/PartActivationHistory.java
private PartServiceImpl partService;
	private EModelService modelService;
	private LinkedList<MPart> generalActivationHistory = new LinkedList<MPart>();
	PartActivationHistory(PartServiceImpl partService, EModelService modelService) {
		this.partService = partService;
		this.modelService = modelService;
	}
	public void clear() {
		generalActivationHistory.clear();
	}
	void activate(MPart part, boolean activateBranch) {
		IEclipseContext context = part.getContext();
		if (activateBranch) {
			context.activateBranch();
		} else {
			IEclipseContext parent = context.getParent();
			do {
				context.activate();
				context = parent;
				parent = parent.getParent();
			} while (parent.get(MWindow.class) != null);
		}
		prepend(part);
	}
	/**
	 * Places the specified part at the end of the activation history if it is not already in the
	 * list. If it is already in the activation history, then its position will not change.