Comment 3 for bug 944053

http://code.google.com/p/rabbitvcs/issues/detail?id=637 fixes
Traceback (most recent call last):
  File "/usr/lib/pymodules/python2.7/rabbitvcs/ui/log.py", line 1296, in compare_previous_revision
    if len(self.revisions[0]["parents"]) > 0:
TypeError: object of type 'NoneType' has no len()