Bug 329482 Uninstantiated part may be rendered when closing another part in the same stack
1. Activate the 'Javadoc' view. 2. Activate the 'Package Explorer' view. 3. Shutdown. 4. Restart. 5. Ctrl+3 > Properties 6. Hide the 'Properties' view. 7. Now the 'Problems' view is the selected element. It should be the 'Javadoc' view.
bundles/org.eclipse.e4.ui.workbench/src/org/eclipse/e4/ui/internal/workbench/PartActivationHistory.java
}
	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);
		}
		queue(part);
	}
	void queue(MPart part) {
		generalActivationHistory.remove(part);
		generalActivationHistory.addFirst(part);
	}
	/**
	 * Checks to see if this element and its parents are actually being rendered.
	 */
	private boolean isValid(MUIElement element) {
		if (element == null || !element.isToBeRendered() || !element.isVisible()) {
			return false;
		}
		if (element instanceof MApplication) {
			return true;
		}
		MUIElement parent = element.getParent();