Game and Details! version
DETAILS! VERSION: BBC31
GAME VERSION 2.5.2

To replicate:
run "/details me" in chat

• Result:
  
  'UnitGroupRolesAssigned (a nill value)'

• Expected
  No error

• When the bug started (a date, wow path release, details update, etc)?
  unknown

• Additional information:
  in slash.lua we have
  elseif (msg == "me" or msg == "ME" or msg == "Me" or msg == "mE") then
  local role = UnitGroupRolesAssigned("player")
  without there being any definition of UnitGroupRolesAssigned

apparently adding
local UnitGroupRolesAssigned = DetailsFramework.UnitGroupRolesAssigned

fixes the issue

With proposed fix I see Player Details! Breakdown screen