Delete tremolo notes result in bad rest

MuseScore 1.0pre2 or trunk

1. Add two half notes in a measure of a 4/4 score
2. Add a double tremolo between the notes
3. Select the second whole note and delete

Expected result : Not sure but not the actual result. I would propose to delete the tremolo, change the first note back to a half note and put a half rest.
Actual result: the note is deleted and replace by a rest of the same size. If you delete both notes, you obtain a two whole rests in a 4/4 measure.