analyze_glitches "ValueError: max() arg is an empty sequence"

See https://ldas-jobs.ligo-la.caltech.edu/~lockloss/events/1239/268071/log:

2019-04-14 04:13:09,668 [analyze.analyze_event] exception in analyze_glitches:
Traceback (most recent call last):
  File "build/bdist.linux-x86_64/egg/locklost/analyze.py", line 48, in analyze_event
    
  File "build/bdist.linux-x86_64/egg/locklost/plugins/glitch.py", line 571, in analyze_glitches
    plot_snr_eventmap(event, triggers, sample_rate, zoom)
  File "build/bdist.linux-x86_64/egg/locklost/plugins/glitch.py", line 456, in plot_snr_eventmap
    channel_snr_max = {ch: max(filt_triggers[ch]['snr']) for ch in channels}
  File "build/bdist.linux-x86_64/egg/locklost/plugins/glitch.py", line 456, in <dictcomp>
    channel_snr_max = {ch: max(filt_triggers[ch]['snr']) for ch in channels}
ValueError: max() arg is an empty sequence