In InstrumentTrack::play(...) the local variable "bb_track" always
was either undefined or NULL due to a lost call (probably during M/V
architecture switch) to bbTrack::findBBTrack(...). This could lead to
crashes and/or misbehaviour when playing frozen patterns in BB tracks.
Signed-off-by: Tobias Doerffel <tobias.doerffel@gmail.com>
(cherry picked from commit fb58dc00ab)