arpegg.py: Fix voices-relaunch crash by keeping a copy of the bound m…

…ethod object.

tulip/shared/py/arpegg.py

@@ -37,6 +37,7 @@ def __init__(self, synth, channel=0):
  self.arpeggiate_base_notes = set()
  self.full_sequence = []
  self.slot = -1
+ self.step_callback = self.arp_step # Ensure bound_method_obj created just once.
 
  def note_on(self, note, vel):
  if not self.active or note >= self.split_note:
@@ -71,7 +72,7 @@ def run(self):
  self.current_step = -1
  # Semaphore to the run loop to start going.
  self.running = True
- self.slot = tulip.seq_add_callback(self.arp_step, int(tulip.seq_ppq()/2))
+ self.slot = tulip.seq_add_callback(self.step_callback, int(tulip.seq_ppq()/2))
 
  def stop(self):
  self.running = False