[BUG] Dirty flag cleared on Undo, but not Redo

[evilc]

Repro:

1. New file
2. Create sketch
3. Draw Rectangle
4. End sketch
5. Extrude rectangle
6. Save
7. Select top face of cube and extrude again
   Project marked as Dirty (*) - CORRECT
8. Undo
   Dirty flag cleared - CORRECT
9. Undo
   Dirty flag set again - CORRECT
10. Redo
    At this point, we are back to where we were on Step 6 (After initial extrude)
    Dirty flag not cleared - INCORRECT
11. Redo then Undo
    Dirty flag cleared - CORRECT
    We are at the same point as we were in Step 10, and the dirty flag is cleared.
    Ergo, the dirty flag is only cleared on an Undo, not on a Redo