Bug 214271 [CommonNavigator] Undo/redo not enabled if nothing selected
bundles/org.eclipse.ui.navigator.resources/src/org/eclipse/ui/internal/navigator/resources/actions/RefactorActionProvider.java
public void init(ICommonActionExtensionSite anActionSite) {
		site = anActionSite;
		refactorGroup = new RefactorActionGroup(site.getViewSite().getShell(), (Tree)site.getStructuredViewer().getControl());
		IUndoContext workspaceContext = (IUndoContext) ResourcesPlugin
				.getWorkspace().getAdapter(IUndoContext.class);
		undoRedoGroup = new UndoRedoActionGroup(((ICommonViewerWorkbenchSite) anActionSite.getViewSite()).getSite(),
				workspaceContext, true);
	}
	public void dispose() {
		undoRedoGroup.dispose();
		refactorGroup.dispose();
	}
	public void fillActionBars(IActionBars actionBars) {
		undoRedoGroup.fillActionBars(actionBars);
		refactorGroup.fillActionBars(actionBars);
	}
	public void fillContextMenu(IMenuManager menu) {
		undoRedoGroup.fillContextMenu(menu);
		refactorGroup.fillContextMenu(menu);
	}
	public void setContext(ActionContext context) {
		undoRedoGroup.setContext(context);
		refactorGroup.setContext(context);
	}
	public void updateActionBars() {
		undoRedoGroup.updateActionBars();
		refactorGroup.updateActionBars();
	}
}