ZeroDivisionError in NaturalBreaksClustering

[ershockley]

There is a ZeroDivisionError in NaturalBreakClustering - full trace here.

So far I have only seen this in the large Kr83m runs that were re-zipped since there were too many files, so I think this might be related to #728 in some way.

This is Run 23830, Event 268443.

To reproduce:

(pax_v6.10.1) [ershockley@login ~]$ rucio download x1t_SR001_181116_1411_tpc:XENON1T-23830-000268000-000268999-000001000.zip --no-subdir --dir 181116_1411 --rse UC_OSG_USERDISK

(pax_v6.10.1) [ershockley@login ~]$ paxer --config XENON1T --input 181116_1411 --output 181116_1411 --event 268443

[ershockley]

I also saw this error in Run 23843, Event 525577.