I'm getting this error constantly in dungeons. Anyone else have this problem?

Code:
Blizzard_InspectUI\InspectPVPFrame.lua:80: Usage: UnitFactionGroup("unit" [,checkDisplayRace])
[C]: in function `UnitFactionGroup'
Blizzard_InspectUI\InspectPVPFrame.lua:80: in function `InspectPVPFrame_Update'
Blizzard_InspectUI\InspectPVPFrame.lua:60: in function <Blizzard_InspectUI\InspectPVPFrame.lua:58>

Locals:
(*temporary) = nil