checkRISK raises KeyError exception when getting score for unknown cve entry not in db

[savon-noir]

...
[warning] Entry CVE-2013-2028 missed from vFeed Database
Traceback (most recent call last):
File "vFeedAPI_calls_1bis.py", line 137, in
cveRISK= vfeed.checkRISK()
File "/tmp/vFeed/lib/vFeedApi.py", line 325, in checkRISK
if self.cvssScore['base'] >= "7.0":
KeyError: 'base'
...