convert: svn: defer get_log parsing until after get_log completes. According to the documentation, it is not safe to perform any other operation on the ra object until get_log completes.

#!/bin/sh
# http://www.selenic.com/mercurial/bts/issue433

hg init a
cd a
echo a > a
hg commit -Ama

hg parents -r 0 doesnotexist
true