use of Ambitus_engraver in DrumStaff causes program crash

[Jesse Engle]

> I'm not top posting.

% use of Ambitus_engraver in DrumStaff causes program crash

\version "2.12.1"

hands = \drummode {
        \repeat unfold 2 {
                cymr8 cymr << cymr sn >> cymr
        }
}

feet = \drummode {
        hhp4 hhp hhp hhp
}

\score {
        \new DrumStaff \with {
                \consists "Ambitus_engraver"
        } <<
                        \new DrumVoice { \voiceOne \hands }
                        \new DrumVoice { \voiceTwo \feet }
        >>
}