Getting the following error during pet battle WQ in Isle of Dorn.

1x .../PetTracker/addons/main/classes/abstract/ability.lua:17: Usage: GetAttackModifier(attackType, defenseType)
[string "=[C]"]: in function GetAttackModifier' [string "@PetTracker/addons/main/classes/abstract/ability.lua"]:17: in function GetModifier'
[string "@PetTracker/addons/main/classes/combat/abilityButton.lua"]:27: in function Display' [string "@PetTracker/addons/main/classes/combat/petSlot.lua"]:72: in function Display'
[string "@PetTracker/addons/battle/switcher.lua"]:78: in function UpdateFor' [string "@PetTracker/addons/battle/switcher.lua"]:68: in function Update'
[string "@PetTracker/addons/battle/switcher.lua"]:28: in function PetBattlePetSelectionFrame_Show' [string "@Blizzard_PetBattleUI/Blizzard_PetBattleUI.lua"]:205: in function PetBattleFrame_UpdatePetSelectionFrame'
[string "@Blizzard_PetBattleUI/Blizzard_PetBattleUI.lua"]:119: in function <Blizzard_PetBattleUI/Blizzard_PetBattleUI.lua:108>

Locals:
(*temporary) = nil
(*temporary) = 10

Yes, it looks like self:GetInfo() sometimes returns type as nil. I did not understand when and why.