Bad median on empty list in sbws generate

pastly@aaseae:~/run/sbws-liveclient-http$ sbws-generate 
2018-07-06 12:59:52,592 DEBUG MainThread globals.py:43 - is_initted - /home/pastly/run/sbws-liveclient-http seems initialized.
2018-07-06 12:59:52,607 DEBUG MainThread filelock.py:17 - __enter__ - Going to lock /home/pastly/run/sbws-liveclient-http/datadir/.lockfile
2018-07-06 12:59:52,607 DEBUG MainThread filelock.py:23 - __enter__ - Received lock /home/pastly/run/sbws-liveclient-http/datadir/.lockfile
2018-07-06 12:59:52,797 DEBUG MainThread filelock.py:27 - __exit__ - Releasing lock /home/pastly/run/sbws-liveclient-http/datadir/.lockfile
2018-07-06 12:59:52,798 DEBUG MainThread resultdump.py:62 - load_result_file - Keeping 2990/3405 read lines from /home/pastly/run/sbws-liveclient-http/datadir/2018-07-06.txt
2018-07-06 12:59:52,805 DEBUG MainThread resultdump.py:85 - trim_results - Keeping 2990/2990 results after removing old ones
Traceback (most recent call last):
  File "/home/pastly/src/simple-bw-scanner/venv-editable/bin/sbws", line 11, in <module>
    load_entry_point('sbws', 'console_scripts', 'sbws')()
  File "/home/pastly/src/simple-bw-scanner/sbws/sbws.py", line 51, in main
    exit(comm['f'](*comm['a'], **comm['kw']))
  File "/home/pastly/src/simple-bw-scanner/sbws/core/generate.py", line 58, in main
    bw_file = V3BWFile.from_arg_results(args, conf, results)
  File "/home/pastly/src/simple-bw-scanner/sbws/lib/v3bwfile.py", line 403, in from_arg_results
    bw_lines = [V3BWLine.from_results(results[fp]) for fp in results]
  File "/home/pastly/src/simple-bw-scanner/sbws/lib/v3bwfile.py", line 403, in <listcomp>
    bw_lines = [V3BWLine.from_results(results[fp]) for fp in results]
  File "/home/pastly/src/simple-bw-scanner/sbws/lib/v3bwfile.py", line 357, in from_results
    bw = cls.bw_from_results(success_results)
  File "/home/pastly/src/simple-bw-scanner/sbws/lib/v3bwfile.py", line 324, in bw_from_results
    r.relay_average_bandwidth for r in results
  File "/usr/lib/python3.5/statistics.py", line 353, in median
    raise StatisticsError("no median for empty data")
statistics.StatisticsError: no median for empty data