Need help with Lua Script error

[Rempage]

Good day all!

I've found a lua script, which checks up for LoS and make delay before next cast, here it is:

if not tLOS then tLOS={} end 
if not fLOS then fLOS=CreateFrame("Frame") end 
delay = 1
function LineOfSight(target) 
fLOS:RegisterEvent("COMBAT_LOG_EVENT_UNFILTERED") 
function fLOSOnEvent(self,event,...) 
if event=="COMBAT_LOG_EVENT_UNFILTERED" then 
local cLOG={...} 
if cLOG and cLOG[2] and cLOG[2]=="SPELL_CAST_FAILED" then 
local player=UnitGUID("player") or "" 
    if cLOG[4] and cLOG[4]==player then 
        if cLOG[15] then 
            if cLOG[15]==SPELL_FAILED_LINE_OF_SIGHT 
            or cLOG[15]==SPELL_FAILED_NOT_INFRONT 
            or cLOG[15]==SPELL_FAILED_OUT_OF_RANGE 
            or cLOG[15]==SPELL_FAILED_UNIT_NOT_INFRONT 
            or cLOG[15]==SPELL_FAILED_UNIT_NOT_BEHIND 
            or cLOG[15]==SPELL_FAILED_NOT_BEHIND 
            or cLOG[15]==SPELL_FAILED_MOVING 
            or cLOG[15]==SPELL_FAILED_IMMUNE 
            or cLOG[15]==SPELL_FAILED_FLEEING 
            or cLOG[15]==SPELL_FAILED_BAD_TARGETS 
            or cLOG[15]==SPELL_FAILED_STUNNED 
            or cLOG[15]==SPELL_FAILED_SILENCED 
            or cLOG[15]==SPELL_FAILED_NOT_IN_CONTROL 
            then 
            tinsert(tLOS,{unit=target,time=GetTime()}) 
            end 
        end 
    end 
else 
if #tLOS > 0 then 
table.sort(tLOS,function(x,y) return x.time>y.time end) 
for i=1,#tLOS do 
local time=tLOS[i].time or GetTime() 
if GetTime()>time+delay then 
tremove(tLOS,i) 
end 
end 
end 
end 
end 
end 
fLOS:SetScript("OnEvent",fLOSOnEvent) 
if #tLOS > 0 then 
for i=1,#tLOS do 
if tLOS and tLOS[i] and tLOS[i].unit==target 
then 
return true 
end 
end 
end 
end

Sometimes it shows errors:

Message: Interface\AddOns\WowAddon4\Frame.lua:87: attempt to index field '?' (a nil value)
Time: 11/13/16 03:10:23
Count: 2
Stack: Interface\AddOns\WowAddon4\Frame.lua:87: in function <Interface\AddOns\WowAddon4\Frame.lua:58>

Locals: self = <unnamed> {
 0 = <userdata>
}
event = "COMBAT_LOG_EVENT_UNFILTERED"
cLOG = <table> {
 1 = 1478995822.928
 2 = "SPELL_PERIODIC_HEAL"
 3 = false
 4 = "Pet-0-1-0-0-69947-00000061D5"
 5 = "Spirit Beast"
 6 = 4369
 7 = 0
 8 = "Player-1-0004DE7A"
 9 = "Старкэ-x100"
 10 = 1297
 11 = 0
 12 = 90361
 13 = "Духовное лечение"
 14 = 8
 15 = 11103
 16 = 0
 17 = 0
 18 = true
 19 = false
}
(for index) = 2
(for limit) = 2
(for step) = 1
i = 2
(*temporary) = nil
(*temporary) = <function> defined =[C]:-1
(*temporary) = <table> {
 1 = <table> {
 }
}
(*temporary) = 1
(*temporary) = "attempt to index field '?' (a nil value)"

87 line is local time=tLOS[i].time or GetTime()
Can anybody help me what is wrong?