LUA errors

[GregoryGH]

7x ...ssionFilter\TradeSkillFrame\Core\DefineFunctions.lua:76: attempt to perform arithmetic on local 'itemLevel' (a nil value)
[string "@SigmaProfessionFilter\TradeSkillFrame\Core\DefineFunctions.lua"]:76: in function GetNumTradeSkills' [string "@SigmaProfessionFilter\TradeSkillFrame\Core\Utility.lua"]:503: in function FullUpdate'
[string "@SigmaProfessionFilter\TradeSkillFrame\Core\DefineFunctions.lua"]:501: in function <...ssionFilter\TradeSkillFrame\Core\DefineFunctions.lua:500>
[string "=[C]"]: ?
[string "=[C]"]: ?
[string "=[C]"]: ?
[string "=[C]"]: in function TradeSkillFrame_OnShow' [string "*:OnShow"]:1: in function <[string "*:OnShow"]:1> [string "=[C]"]: ? [string "=[C]"]: in function Show'
[string "@Interface_TBC\FrameXML\UIParent.lua"]:2105: in function SetUIPanel' [string "@Interface_TBC\FrameXML\UIParent.lua"]:1950: in function ShowUIPanel'
[string "@Interface_TBC\FrameXML\UIParent.lua"]:1818: in function <Interface_TBC\FrameXML\UIParent.lua:1814>