potential error in retrieving data from circular buffer

[vstadnytskyi]

Exception in thread Thread-1:
Traceback (most recent call last):
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/threading.py", line 926, in _bootstrap_inner
    self.run()
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/threading.py", line 870, in run
    self._target(*self._args, **self._kwargs)
  File "/Users/femto-13/All-Projects-on-femto/LaserLab/Software/libraries/icarus-nmr/icarus_nmr/event_handler.py", line 514, in run
    self.run_once()
  File "/Users/femto-13/All-Projects-on-femto/LaserLab/Software/libraries/icarus-nmr/icarus_nmr/event_handler.py", line 538, in run_once
    self.evaluate_events()
  File "/Users/femto-13/All-Projects-on-femto/LaserLab/Software/libraries/icarus-nmr/icarus_nmr/event_handler.py", line 1243, in evaluate_events
    self.push_target_pressure()
  File "/Users/femto-13/All-Projects-on-femto/LaserLab/Software/libraries/icarus-nmr/icarus_nmr/event_handler.py", line 1371, in push_target_pressure
    target_pressure = scipy.stats.mode(data[:,0])[0][0]
IndexError: index 0 is out of bounds for axis 0 with size 0

The function that fails is this:

  def get_ring_buffer_N(self,N,pointer):
       #print('input: N= %r ; pointer = %r )' % (N, pointer))
       if pointer > (self.packet_buffer_size+1)*self.packet_length:
           pointer = int(pointer - ((self.packet_buffer_size+1)*self.packet_length)-1)
       # try:
           #print(' try: N= %r ; pointer = %r' % (N, pointer))
       res = self.circular_buffer.get_N(N, pointer)
       # except:
       #     res = nan
       return res

N = 400, pointer = unknown.