TypeError: 'NoneType' object is not iterable

[fgeek]

Fuzzed sample: http://bugs.fi/media/afl/enzyme/enzyme-015.mkv
Fuzzers used: http://lcamtuf.coredump.cx/afl/ https://bitbucket.org/jwilk/python-afl
SHA1: eab6f36c7c16b06cfc350e0f9e04f334d075642f

mkvinfo.py:

import sys
import enzyme
inputfile = sys.argv[1]
try:
    with open(inputfile, 'rb') as f:
        mkv = enzyme.MKV(f)
    print(mkv.info)
    print(mkv.video_tracks)
    print(mkv.audio_tracks)
except enzyme.exceptions.MalformedMKVError:
    pass

Traceback (most recent call last):
  File "mkvinfo.py", line 8, in <module>
    mkv = enzyme.MKV(f)
  File "/usr/local/lib/python2.7/dist-packages/enzyme-0.4.1-py2.7.egg/enzyme/mkv.py", line 54, in __init__
    self._parse_seekhead(seek_head, segment, stream, specs)
  File "/usr/local/lib/python2.7/dist-packages/enzyme-0.4.1-py2.7.egg/enzyme/mkv.py", line 74, in _parse_seekhead
    self.video_tracks.extend([VideoTrack.fromelement(t) for t in tracks if t['TrackType'].data == VIDEO_TRACK])
TypeError: 'NoneType' object is not iterable