#1 performance.py error when no positives (true or false) exist

[Greg C]

An uncaught exception occurs in pretty_precision_recall_fmeasure() in performance.py when precision and recall are both 0.0.

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Extracted Mentions
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0.0 0.0 None
Traceback (most recent call last):
File "/Applications/MutationFinder/performance.py", line 487, in <module>
calculate_extracted_mentions(extractor_output))
File "/Applications/MutationFinder/performance.py", line 193, in __str__
self.pretty_precision_recall_fmeasure()])
File "/Applications/MutationFinder/performance.py", line 187, in pretty_precision_recall_fmeasure
% {'pre':self._p,'re':self._r,'fm':self._f})
TypeError: float argument required