Lua 错误：字符串预期，但却得到了 nil。

我需要帮助我的脚本。 我尝试了几乎所有方法，但我无法弄清楚问题出在哪里。 我想让 look.lua 检查是否 str = str.."\nIt's "..getPokemonAge(thing.uid).." old." 返回 nil，然后忽略它，并继续执行脚本。

这是我在控制台上得到的错误：

[04/12/2012 20:43:42] [Error - CreatureScript Interface]
[04/12/2012 20:43:42] data/creaturescripts/scripts/look.lua:onLook
[04/12/2012 20:43:42] Description:
[04/12/2012 20:43:42] data/lib/011-string.lua:16: bad argument #1 to 'find' (string expected, got nil)
[04/12/2012 20:43:42] stack traceback:
[04/12/2012 20:43:42]   [C]: in function 'find'
[04/12/2012 20:43:42]   data/lib/011-string.lua:16: in function '(for generator)'
[04/12/2012 20:43:42]   data/lib/011-string.lua:16: in function 'explode'
[04/12/2012 20:43:42]   data/lib/age system.lua:2: in function 'getPokemonYears'
[04/12/2012 20:43:42]   data/lib/age system.lua:42: in function 'getPokemonAge'
[04/12/2012 20:43:42]   data/creaturescripts/scripts/look.lua:32: in function <data/creaturescripts/scripts/look.lua:1>

011-string.lua

local i, pos, tmp, t = 0, 1, "", {}
        for s, e in function() return string.find(str, sep, pos) end do
            tmp = str:sub(pos, s - 1):trim()
            table.insert(t, tmp)
            pos = e + 1

            i = i + 1

        end

look.lua

str = str.."\nIt's "..getPokemonAge(thing.uid).." old."

age system.lua

function getPokemonYears(pokeball)
local data = string.explode(getItemAttribute(pokeball, "pokeballinfo"), "/")
-- data[1] = dia, data[2] = mes, data[3] = ano
local yearnow = math.floor(tonumber(os.date("%Y")))
local monthnow = math.floor(tonumber(os.date("%m")))
local daynow = math.floor(tonumber(os.date("%d")))
local ano = math.floor(tonumber(data[3]))
local mes = math.floor(tonumber(data[2]))
local dia = math.floor(tonumber(data[1]))
local years = 0
if yearnow == ano then years = monthnow-mes end
if yearnow > ano then years = (12-mes) + monthnow end
return years
end

function getPokemonMonths(pokeball)
local data = string.explode(getItemAttribute(pokeball, "pokeballinfo"), "/")
local yearnow = math.floor(tonumber(os.date("%Y")))
local monthnow = math.floor(tonumber(os.date("%m")))
local daynow = math.floor(tonumber(os.date("%d")))
local ano = math.floor(tonumber(data[3]))
local mes = math.floor(tonumber(data[2]))
local dia = math.floor(tonumber(data[1]))

if (yearnow == ano) and (monthnow==mes) and (daynow<dia+2.5) then months = 0 end
if (yearnow == ano) and (monthnow==mes) and (daynow>dia+2.5) then months = (daynow-dia)/2.5 end
if (yearnow == ano) and (monthnow>mes) then months = math.floor((30-dia)/2.5) + daynow/2.5 end
if (yearnow > ano) then
days = math.floor(monthnow*30+daynow)
months = math.floor(days/2.5)
end
if tostring(months):len() > 3 then months2 = tonumber(string.sub(tostring(months), 1, 3))
else months2 = months end
return months
end

function getPokemonAge(pokeball)
return ""..getPokemonYears(pokeball).." year, "..getPokemonMonths(pokeball).." months"
end