Notes missing in MIDI output

[Nick Prömper]

Hi all!

I figured out a problem with the midi output. If you enter a crescendo without 
giving anabsolute dynamic, lilypond sets the volume down to zero.

Is that a known bug, or a feature ;-) ? Is there a work-around (without giving 
absolute dynamics?)

\version "2.8.1"

\header {
        title = "Notes missing"
}
Trompe = \new Staff \relative c' {
        
        c4 d\< e f g a b\! c
        %{ that works: c4 d\p\< e f g a b\f c %}
}
\score {
        \Trompe
        \layout {
                indent = 2\cm
        }
}
\score {
        \Trompe
        \midi {
        }
}