In both the release and beta versions of Spartan UI, I get an error when I try and also load Family Familiar Helper. I reported it there as the stack trace seems to be tied to it, but it only happens when I also have Spartan UI loaded as well:

Message: Interface\SharedXML\Util.lua:192: bad argument #1 to 'pairs' (table expected, got nil)
Time: Mon Jun 25 00:25:11 2018
Count: 1
Stack: Interface\SharedXML\Util.lua:192: bad argument #1 to 'pairs' (table expected, got nil)
[C]: in function pairs' Interface\SharedXML\Util.lua:192: in function CopyTable'
...AddOns\FamilyFamiliarHelper\FamilyFamiliarHelper.lua:358: in function `?'
...AddOns\FamilyFamiliarHelper\FamilyFamiliarHelper.lua:346: in function <...AddOns\FamilyFamiliarHelper\FamilyFamiliarHelper.lua:345>

Locals: (*temporary) = nil
(*temporary) = "table expected, got nil"
= defined =[C]:-1

The issue is that Family Familiar is trying to modify the background of tooltips and assumes they have a backdrop. SpartanUI removes the backdrop causing Family Familiar to break. Family Familiar needs to tweak their code to account for this as i am sure other tooltip addons remove that backdrop as well.

A work around would be to edit Family Familiar:

Find this code:

   ffh.oldTooltipBackdrop = GameTooltip:GetBackdrop()
   ffh.newTooltipBackdrop = CopyTable(ffh.oldTooltipBackdrop)
   ffh.newTooltipBackdrop.bgFile = "Interface\\ChatFrame\\ChatFrameBackground"

Replace it with this:

   ffh.oldTooltipBackdrop = GameTooltip:GetBackdrop()
   if ffh.oldTooltipBackdrop then
	   ffh.newTooltipBackdrop = CopyTable(ffh.oldTooltipBackdrop)
	   ffh.newTooltipBackdrop.bgFile = "Interface\\ChatFrame\\ChatFrameBackground"
   end 

Let me know if the above code does not function as intended I am not able to test it at this time.

It worked... thank you!