IndexError: list index out of range in def check_avg_time

[Joshwannaknow]

Traceback (most recent call last):
  File "/usr/lib/python3.8/threading.py", line 932, in _bootstrap_inner
    self.run()
  File "/usr/lib/python3.8/threading.py", line 870, in run
    self._target(*self._args, **self._kwargs)
  File "/home/lab702/SniffnDetect/sniffndetect.py", line 41, in analyze_threader
    self.analyze_packet(pkt)
  File "/home/lab702/SniffnDetect/sniffndetect.py", line 80, in analyze_packet
    self.set_flags()
  File "/home/lab702/SniffnDetect/sniffndetect.py", line 63, in set_flags
    self.FILTERED_ACTIVITIES[category]['flag'] = self.check_avg_time(
  File "/home/lab702/SniffnDetect/sniffndetect.py", line 48, in check_avg_time
    time += activities[c][0] - activities[c-1][0]
IndexError: list index out of range

hi~
I just install the modules and run the code it give me a error pls help
I use this code on Ubuntu