Bug 189636 Custom rule template failing
Null poonter exception being thrown when trying to add a custom rule which is causing the rule cretion to fail. Also there is a minor typo in the rule template string.
bundles/org.eclipse.ui.navigator/src/org/eclipse/ui/internal/navigator/NavigatorContentService.java
* viewer is determined by the ID used to create the
	 * INavigatorContentService ({@link #getViewerId() }). See
	 * {@link #createCommonContentProvider() } for more information about how
	 * content providers are located for the root of the viewer. The root
	 * content providers are calculated once. If a new element is supplied, a
	 * client must call {@link #update() } prior in order to reset the
	 * calculated root providers.
	 * </p>
	 * 
	 * @param anElement
	 *            An element from the tree (generally the input of the viewer)
	 * @return The set of content providers that can provide root elements for a
	 *         viewer.
	 */
	public ITreeContentProvider[] findRootContentProviders(Object anElement) {
		if (rootContentProviders != null) {
			return rootContentProviders;
		}
		synchronized (this) {
			if (rootContentProviders == null) {
				rootContentProviders = extractContentProviders(findRootContentExtensions(anElement));
			}
		}
		return rootContentProviders;
	}
	/**
	 * 
	 * Return all of the label providers that are enabled for the given element.
	 * A label provider is 'enabled' if its corresponding content provider
	 * returned the element, or the element is described in the content