Fixed NSUndoManager allocation bug.
This sample illustrates a number of aspects of working with the Core Data framework with an iOS application:
* Use of an instance of NSFetchedResultsController object to manage a collection of objects to be displayed in a table view.
* Undo and redo.
* Database initialization.
* Use of a second (child) managed object context to isolate changes during an add operation.
Signed-off-by: Liu Lantao <liulantao@gmail.com>
6196905afd