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
* (non-Javadoc)
	 * 
	 * @see org.eclipse.ui.navigator.INavigatorContentService#createCommonDescriptionProvider()
	 */
	public IDescriptionProvider createCommonDescriptionProvider() {
		if (descriptionProvider != null) {
			return descriptionProvider;
		}
		synchronized (this) {
			if (descriptionProvider == null) {
				descriptionProvider = new NavigatorContentServiceDescriptionProvider(
						this);
			}
		}
		return descriptionProvider;
	}
	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.ui.internal.navigator.INavigatorContentService#dispose()
	 */
	public void dispose() {
		if (navigatorSaveablesService != null) {
			assistant.removeListener(navigatorSaveablesService);
		}
		for (Iterator contentItr = contentExtensions.values().iterator(); contentItr
				.hasNext();) {
			((NavigatorContentExtension) contentItr.next()).dispose();
		}
		getActivationService().removeExtensionActivationListener(this);