Open Radar

 
Summary: 
A text view's undos interacts with Core Data undos confusing the undo manager resulting in it constantly returning YES for -canUndo, even after the undo stack is exhausted.

Steps to Reproduce:
1) Run the attached application.
2) Click the "Add" button to add a person
3) Click in the "Last Name" text view (not the text field)
4) Make some edits
5) Click in the "Last Name" text field
6) Click back into the text view
7) Make some more edits
8) Hit Undo 6 times

Expected Results:
The undo stack should be empty after twice hitting Undo.

Actual Results:
The undo stack is never empty, and you can hit Undo forever.  The same goes for Redo.  You can keep doing Redo, after the redo stack is empty.

Regression:
I've tested on 10.5 (10.5.6/9J61) and 10.6 (10A380).

Notes:
Attached is a sample project (Editor2.tbz).  There is no workaround for this problem, that I know of.