Bug 296253 [CommonNavigator] An empty label is not properly shown when it is the only contributed label
bundles/org.eclipse.ui.navigator/src/org/eclipse/ui/internal/navigator/NavigatorContentServiceLabelProvider.java
* @see org.eclipse.jface.viewers.IBaseLabelProvider#addListener(org.eclipse.jface.viewers.ILabelProviderListener)
	 */
	public void addListener(ILabelProviderListener aListener) {
		addListenerObject(aListener);
	}
	/**
	 * <p>
	 * Label provider listeners are currently supported.
	 * </p>
	 * 
	 * {@inheritDoc}
	 * @see org.eclipse.jface.viewers.IBaseLabelProvider#removeListener(org.eclipse.jface.viewers.ILabelProviderListener)
	 */
	public void removeListener(ILabelProviderListener aListener) {
		removeListenerObject(aListener);
	}
	/**
	 * <p>
	 * Dispose of the content service, if it was created and not supplied.
	 * </p>
	 * <p>
	 * <b>If a client uses this class outside of the framework of {@link CommonViewer}, this method
	 * must be called when finished. </b>
	 * </p>
	 * 
	 * {@inheritDoc}
	 * @see org.eclipse.jface.viewers.IBaseLabelProvider#dispose()
	 */
	public void dispose() {
		if (isContentServiceSelfManaged) {