Some Vzaar videos do not download; stack trace

[cjfsyntropy]

Although I have successfully download three Vzaar videos today, this one will not download (but I was able to download it Firefox; it also failed with youtube-dl version 2019.06.21):

youtube-dl -v -o "Week1.05.%(title)s-%(id)s.%(ext)s" https://view.vzaar.com/20313539/download
[debug] System config: []
[debug] User config: []
[debug] Custom config: []
[debug] Command-line args: [u'-v', u'-o', u'Week1.05.%(title)s-%(id)s.%(ext)s', u'https://view.vzaar.com/20313539/download']
[debug] Encodings: locale UTF-8, fs UTF-8, out UTF-8, pref UTF-8
[debug] youtube-dl version 2019.07.02
[debug] Python version 2.7.16 (CPython) - Linux-4.19.0-5-amd64-x86_64-with-debian-10.0
[debug] exe versions: ffmpeg 4.1.3-1, ffprobe 4.1.3-1, phantomjs 2.1.1, rtmpdump 2.4
[debug] Proxy map: {}
[Vzaar] 20313539: Downloading JSON metadata
[Vzaar] 20313539: Downloading m3u8 information
[debug] Default format spec: bestvideo+bestaudio/best
Traceback (most recent call last):
File "/usr/lib/python2.7/runpy.py", line 174, in _run_module_as_main
"main", fname, loader, pkg_name)
File "/usr/lib/python2.7/runpy.py", line 72, in _run_code
exec code in run_globals
File "/home/cjf/bin/youtube-dl/main.py", line 19, in
File "/home/cjf/bin/youtube-dl/youtube_dl/init.py", line 474, in main
File "/home/cjf/bin/youtube-dl/youtube_dl/init.py", line 464, in _real_main
File "/home/cjf/bin/youtube-dl/youtube_dl/YoutubeDL.py", line 2008, in download
File "/home/cjf/bin/youtube-dl/youtube_dl/YoutubeDL.py", line 807, in extract_info
File "/home/cjf/bin/youtube-dl/youtube_dl/YoutubeDL.py", line 861, in process_ie_result
File "/home/cjf/bin/youtube-dl/youtube_dl/YoutubeDL.py", line 1642, in process_video_result
File "/home/cjf/bin/youtube-dl/youtube_dl/YoutubeDL.py", line 1707, in process_info
TypeError: object of type 'NoneType' has no len()