factoid modification of non-existent factoid throws exception

[Stefano Rivera]

21:36 <&Gargablegar> tibid 1*pi is to much pie
21:36 < tibid> Gargablegar: I'll remember that
21:37 <@tumbleweed> tibid: 1*py ~= s/to/too/
21:37 < tibid> tumbleweed: That didn't go down very well. Burp.

ERROR:scripts.ibid-plugin:Exception occured in Modify processor of factoid plugin
Traceback (most recent call last):
  File "scripts/ibid-plugin", line 129, in <module>
    processor.process(event)
  File "./ibid/plugins/__init__.py", line 119, in process
    method(event, *match.groups())
  File "./ibid/plugins/factoid.py", line 624, in modify
    if len(factoids) == 0:
TypeError: object of type 'NoneType' has no len()