TypeError: 'NoneType' object is not iterable

[sentry-io]

Sentry Issue: TWITTER-SAUCEBOT-F

KeyError: 0
  File "twsaucenao/sauce.py", line 46, in get
    return self._sauce_cache[index]

TypeError: 'NoneType' object is not iterable
(2 additional frame(s) were not displayed)
...
  File "twsaucenao/sauce.py", line 48, in get
    self._sauce_cache[index] = await self._get_sauce(index)
  File "twsaucenao/sauce.py", line 63, in _get_sauce
    sauce_results = await self.sauce.from_file(io.BytesIO(file))
  File "pysaucenao/saucenao.py", line 88, in from_file
    return SauceNaoResults(response, self._min_similarity, self._priority, self._priority_tolerance, self._loop)
  File "pysaucenao/containers.py", line 82, in __init__
    self._sort_results()
  File "pysaucenao/containers.py", line 122, in _sort_results
    self._results = [r for r in self._results if float(r['header']['similarity']) > self._min_similarity]

[saucenaopls] An unknown error occurred while processing tweet 1389271230625222657