When looking up albums on MB that have no release events, the musicbrainz-tool fetches nothing and errs out with:
Can't call method "count" on an undefined value at /usr/bin/abcde-musicbrainz-tool line 99.
And indeed, changing line 99 to
if ($release->release_event_list() and $release->release_event_list()->count() > 0)
solves the problem.
I think this is fixed in git now...
*** This bug has been marked as a duplicate of bug 57 ***