Fix small reference problems

[ckcollab]

• [ ] _"UnboundLocalError: local variable ‘overallranks’ referenced before assignment"

  File "/app/codalab/apps/web/views.py", line 522, in get
  return super(CompetitionDetailView, self).get(request, *args, **kwargs)
  File "/usr/local/lib/python2.7/site-packages/django/views/generic/detail.py", line 111, in get
  context = self.get_context_data(object=self.object)
  File "/app/codalab/apps/web/views.py", line 570, in get_context_data
  scores = context['active_phase'].scores()
  File "/app/codalab/apps/web/models.py", line 1234, in scores
  ranked_submissions = sorted(submission_ids, cmp=CompetitionPhase.rank_submissions(overall_ranks))
  UnboundLocalError: local variable ‘overall_ranks’ referenced before assignment

• [ ] _"UnboundLocalError: local variable ‘overallranks’ referenced before assignment"

  File "/app/codalab/apps/web/views.py", line 1346, in get_context_data
  scores = active_phase.scores(include_scores_not_on_leaderboard=True)
  File "/app/codalab/apps/web/models.py", line 1234, in scores
  ranked_submissions = sorted(submission_ids, cmp=CompetitionPhase.rank_submissions(overall_ranks))
  UnboundLocalError: local variable ‘overall_ranks’ referenced before assignment

• [x] "DoesNotExist: CompetitionSubmission matching query does not exist."

File "/app/codalab/apps/web/views.py", line 1266, in get
  submission = models.CompetitionSubmission.objects.get(pk=kwargs.get('submission_id'))
File "/usr/local/lib/python2.7/site-packages/django/db/models/manager.py", line 151, in get
  return self.get_queryset().get(*args, **kwargs)
File "/usr/local/lib/python2.7/site-packages/django/db/models/query.py", line 310, in get
  self.model._meta.object_name)
DoesNotExist: CompetitionSubmission matching query does not exist.

[Didayolo]

Do we know the context of this? How to reproduce this problems?

[Didayolo]

https://github.com/codalab/codalab-competitions/blob/eb1059ed9fd227f85f0398d9ebf21967d4c551dc/codalab/apps/web/models.py#L1233