[공통] 들이치기 매크로 쓰는데 자꾸 lua 오류나네요

이렇게 매크로 쓰고있는데 루아오류가 계속 나서요 잘아시는분들좀 봐주세요 ㅠㅠ

#showtooltip 들이치기

/run c="들이치기"t="target"b=UnitCastingInfo(t)d=UnitChannelInfo(t);b=b or d;a=UnitName(t)if a and GetSpellCooldown(c)==0 then s=""if b then s="차단성공"else s="차단실패" end;SendChatMessage(a.." "..b.." "..s)end;

/시전 들이치기

아래는 lua 오류메세지 입니다 .ㅠ 에드온은 없으며 기본쓰고있습니다.

Message: [string "c="들이치기"t="target"b=UnitCastingInfo..."]:1: attempt to concatenate global 'b' (a nil value)

Time: Fri Oct 19 16:34:28 2018

Count: 1

Stack: [string "c="들이치기"t="target"b=UnitCastingInfo..."]:1: attempt to concatenate global 'b' (a nil value)

[string "c="들이치기"t="target"b=UnitCastingInfo..."]:1: in main chunk

[C]: in function `RunScript'

InterfaceFrameXMLChatFrame.lua:2158: in function `?'

InterfaceFrameXMLChatFrame.lua:4734: in function `ChatEdit_ParseText'

InterfaceFrameXMLChatFrame.lua:4396: in function `ChatEdit_SendText'

InterfaceFrameXMLChatFrame.lua:2884: in function <InterfaceFrameXMLChatFrame.lua:2877>

[C]: in function `UseAction'

InterfaceFrameXMLSecureTemplates.lua:345: in function `handler'

InterfaceFrameXMLSecureTemplates.lua:623: in function `SecureActionButton_OnClick'

InterfaceFrameXMLMultiActionBars.lua:24: in function `MultiActionButtonUp'

[string "MULTIACTIONBAR2BUTTON8"]:4: in function <[string "MULTIACTIONBAR2BUTTON8"]:1>

Locals: (*temporary) = <function> defined =[C]:-1

(*temporary) = "아드하라 화이트"

(*temporary) = " "

(*temporary) = nil

(*temporary) = " 차단실패"

(*temporary) = "차단실패"

(*temporary) = "attempt to concatenate global 'b' (a nil value)"