Repro is with Zui commit de25266.

The attached video shows the import of the sample.zng data from this repo. As it shows, the default histogram is rendered with Error(missing) for all of the values. A sniff in Wireshark shows the the query being sent to the lake API from here:

Looks like this (note the undefined):

{"query":"from 'sample.zng' | ts != null | count() by time := bucket(ts, 100ms), group := undefined | sort time"}