请问魔兽世界里的插件-大脚错误报告这个什么意思？

Interface尀AddOns尀SpellHelper尀SpellHelper.lua:1: attempt to index local ✀self✀ (a nil value)The version of interface is: 2.4.0110.CALLSTACK==>Interface尀AddOns尀BigFoot尀BigFootError.lua:1: in function `BIGFOOT_ERRORMESSAGE✀Interface尀AddOns尀BigFoot尀BigFootError.lua:1: in function <Interface尀AddOns尀BigFoot尀BigFootError.lua:1>[C]: ?Interface尀AddOns尀SpellHelper尀SpellHelper.lua:1: in function `SpellHelperButton_OnEnter✀Interface尀AddOns尀SpellHelper尀SpellHelper.lua:1: in function `SpellHelperButton_OnUpdate✀[string "*:OnUpdate"]:1: in function <[string "*:OnUpdate"]:1>什么意思啊？？？？？