[Rilgamon]

Not sure. I'm not good with the secure handling of scripts.
I'd either track down exactly the events that lead to the construction of the frame and copy them
or I'd add checks if the frame exists before I use it which is always a good idea when you dont own a frame.

frameHandler:SetScript("OnEvent", function(self, event, ...) -- Hides/shows frames when leaving/entering combat
  if PitBull4_Groups_Party then  
    if event =="PLAYER_REGEN_DISABLED" then
        inCombat = true
        PitBull4_Groups_Party:Show()
    else
        inCombat = false
        PitBull4_Groups_Party:Hide()
    end
  end
end)