[Trunk] Closing score with part via shortcut does nothing

1. Open score.
2. Open 'Parts'.
3. Create part.
4. Close 'Parts'.
5. Open the part.
6. Using shortcut, close the score.

Expected result: Dialogue box appears offering to either 'Don't Save', 'Cancel' or 'Save'.
Actual result: No box appears.

Discussion: This only applies to the part, not the full score.

Using MuseScore 2.0 Nightly Build (4961) - Mac 10.6.8.