[Trunk] Dragging rest to ledger lines and undo doesn't produce stave rest

1. Create score.
2. Drag bar rest to a place of ledger lines.
3. Undo.

Expected result: Stave rest (image ).
Actual result: Ledger rest (image ).

Workaround: Reset will produce a stave rest.

Using MuseScore 2.0 Nightly Build (4903) - Mac 10.6.8.