Drag-and-drop percussion crash

1. Create new score with percussion clef (5-line staff), 4/4 time
2. In measure 1 select the whole measure rest
3. In the note entry tool bar click "half note" to split the whole measure rest into two
4. Drag-and-drop bass drum to first half-note rest
5. Drag-and-drop bass drum to second half-note rest

MuseScore crashes.

(Tested using r.1869, Windows XP)

First reported by Xavierjazz: http://musescore.org/en/node/1631