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/advanced/provider/PlaceholderItemProvider.java
import org.eclipse.emf.edit.provider.IItemPropertyDescriptor;
import org.eclipse.emf.edit.provider.IItemPropertySource;
import org.eclipse.emf.edit.provider.IStructuredItemContentProvider;
import org.eclipse.emf.edit.provider.ITreeItemContentProvider;
/**
 * This is the item provider adapter for a {@link org.eclipse.e4.ui.model.application.ui.advanced.MPlaceholder} object.
 * <!-- begin-user-doc -->
 * <!-- end-user-doc -->
 * @generated
 */
public class PlaceholderItemProvider
	extends UIElementItemProvider
	implements
		IEditingDomainItemProvider,
		IStructuredItemContentProvider,
		ITreeItemContentProvider,
		IItemLabelProvider,
		IItemPropertySource {
	/**
	 * This constructs an instance from a factory and a notifier.
	 * <!-- begin-user-doc -->
	 * <!-- end-user-doc -->
	 * @generated
	 */
	public PlaceholderItemProvider(AdapterFactory adapterFactory) {
		super(adapterFactory);
	}
	/**
	 * This returns the property descriptors for the adapted class.
	 * <!-- begin-user-doc -->