Bug 317405 [Model] HandledItem should be abstract
Looks like an oversight the only real types are HandledMenuItem and HandledToolItem.
bundles/org.eclipse.e4.ui.model.workbench.edit/src/org/eclipse/e4/ui/model/application/ui/menu/provider/MenuItemProviderAdapterFactory.java
* @generated
	 */
	@Override
	public boolean isFactoryForType(Object type) {
		return supportedTypes.contains(type) || super.isFactoryForType(type);
	}
	/**
	 * This implementation substitutes the factory itself as the key for the adapter.
	 * <!-- begin-user-doc -->
	 * <!-- end-user-doc -->
	 * @generated
	 */
	@Override
	public Adapter adapt(Notifier notifier, Object type) {
		return super.adapt(notifier, this);
	}
	/**
	 * <!-- begin-user-doc -->
	 * <!-- end-user-doc -->
	 * @generated
	 */
	@Override
	public Object adapt(Object object, Object type) {
		if (isFactoryForType(type)) {
			Object adapter = super.adapt(object, type);
			if (!(type instanceof Class<?>) || (((Class<?>)type).isInstance(adapter))) {
				return adapter;
			}
		}
		return null;