Bug: Replaying problem interaction events

[bmtcril]

Some problems interaction events fail on tracking log replay. We should investigate the proposed fix here to make sure it works for all expected cases: #301 (comment)

[bmtcril]

Specifically we're seeing the following in tracking logs that need to be handled:

"weighted_possible": 0

  File "/openedx/venv/lib/python3.8/site-packages/event_routing_backends/processors/xapi/event_transformers/problem_interaction_events.py", line 160, in get_result
    'scaled': event_data['weighted_earned']/event_data['weighted_possible']

"max_grade": 0

  File "/openedx/venv/lib/python3.8/site-packages/event_routing_backends/processors/mixins/base_transformer.py", line 105, in transform
    value = getattr(self, f'get_{key}')()
  File "/openedx/venv/lib/python3.8/site-packages/event_routing_backends/processors/xapi/event_transformers/problem_interaction_events.py", line 270, in get_result
    'scaled': event_data.get('grade', None) / event_data.get('max_grade', None)
ZeroDivisionError: division by zero