I did a search and doesnt appear the MOD author started a thread, so putting this here to hopefully catch their attentiion.
PetExtend\Core.lua:277: attempt to concatenate field `cost' (a nil value)
PetExtend\Core.lua:277: in function `Scan'
PetExtend\Core.lua:200: in function `obj_method'
AceEvent\AceEvent-2.0.lua:312: in function `TriggerEvent'
AceEvent\AceEvent-2.0.lua:898: in function <...\AddOns\ag_UnitFrames\libs\AceEvent\AceEvent-2.0.lua:890>
I tried updating ag_UnitFrames but theres nothing to update.
Also, the mod appears to be saving settings when looking at the SV, but on login, all settigns are working at default.