Drop notes with length zero

[jasp00]

Beat notes (length < 0) are not erased, they are turned into hidden notes (length == 0) that allow to restore velocity and key. This is a problem when editing the pattern in the piano roll, because there may be two notes on the same position. If one note is hidden and the other is not within the same position, what should the BB editor do?

Notes with length zero should be visible somehow and there should be an easy way to erase beat notes. To sum up, current behavior is too complicated and notes with length zero should be dropped.