gm-unit > Skills: reports for skills at level 20 don't report correctly; dfhack 50.13-r2

[Scrapulous]

When I start gm-unit and look at the Skills screen while a character with multiple skills at 20 is selected, the skills report looks wrong. For example:
Fighting: nil 40 4419/0
Observation: nil 73 706/0

But other >15 skills seem to be handled fine:
Brewing: Legendary+2 17 2032/2200

My expectation is that level 20 skills would follow the same format, i.e:
Fighting: Legendary+5 20 4419/[whatever]

Repro steps:

1. select a character with a skill at 20 (verified in my case using Dwarf Therapist)
2. start gm-unit
3. select the Skills page
4. scroll to the level 20 skill, observe the problem