[MusicXML] [1.2] Bad pitch and alter exported for cross staff note

MuseScore 1.1 and current branch (not tested in trunk)

1. Open the attached score
2. Save as MusicXML
3. Open the resulting MusicXML file

Actual result: The notes from the F clef moved to the G clef are not exported correctly. In the MusicXML file, you can see that pitch is wrong and alter value is 8 or 9.