Streak worker exception: going over cursor/list bounds

[davidwilemski]

Traceback (most recent call last):
  File "/home/david/orl_env/local/lib/python2.7/site-packages/rq/worker.py", line 429, in perform_job
    rv = job.perform()
  File "/home/david/orl_env/local/lib/python2.7/site-packages/rq/job.py", line 348, in perform
    self._result = self.func(*self.args, **self.kwargs)
  File "/home/david/orl_env/local/lib/python2.7/site-packages/openrunlog/rqworkers.py", line 22, in calculate_streaks
    user.calculate_streaks(r)
  File "/home/david/orl_env/local/lib/python2.7/site-packages/openrunlog/models.py", line 252, in calculate_streaks
    self.streaks = self._calculate_streaks(runs)
  File "/home/david/orl_env/local/lib/python2.7/site-packages/openrunlog/models.py", line 276, in _calculate_streaks
    delta = relativedelta(runs[i+1].date, runs[i].date)
  File "/home/david/orl_env/local/lib/python2.7/site-packages/mongoengine/queryset/base.py", line 150, in __getitem__
    return queryset._document._from_son(queryset._cursor[key],
  File "/home/david/orl_env/local/lib/python2.7/site-packages/pymongo/cursor.py", line 472, in __getitem__
    raise IndexError("no such item for Cursor instance")
IndexError: no such item for Cursor instance