[Sythalin]

Getting an error that I don't know how to resolve:

-- SET CITIES --
function MageTaxi:SetFaction()
    if UnitFactionGroup("player") == "Alliance" then
        cityList = {
            [1] = "Stormwind",
            [2] = "Ironforge",
            [3] = "Darnassus",
            [4] = "Exodar",
            [5] = "Theramore",
            [6] = "Shattrath",
            [7] = "Dalaran",
        }
    else
        cityList = {
            [1] = "Undercity",
            [2] = "Orgrimmar",
            [3] = "Thunder Bluff",
            [4] = "Silvermoon",
            [5] = "Stonard",
            [6] = "Shattrath",
            [7] = "Dalaran"
        }
    end;
        dest = cityList[1]
end
 
-- SET DESTINATION --
local function setLoc(i)
    for num= 1,#cityList do
        _G["MageTaxi_City".. num]:SetChecked(false)  -- line 91
    end
    dest = cityList[i]
    _G["MageTaxi_City".. i]:SetChecked(true)
end
 
function MageTaxi_createGUI()
    -- other code
    for i = 1,#cityList do
        cb = CreateFrame("CHECKBUTTON", "MageTaxi_City"..i, f, "UIRadioButtonTemplate")
            if i == 1 then
                cb:SetPoint("TOPLEFT", f, "TOPLEFT", 40, -45)
            else
                cb:SetPoint("TOP", "MageTaxi_City".. (i-1), "BOTTOM", 0, -10)
            end
            cb:SetScript("OnClick", setLoc(i)) -- line 149
        end
end

Message: Interface\AddOns\MageTaxi\magetaxi.lua:91: attempt to index field '?' (a nil value)
Time: 02/09/10 21:08:49
Count: 1
Stack: Interface\AddOns\MageTaxi\magetaxi.lua:91: in function <Interface\AddOns\MageTaxi\magetaxi.lua:89>
Interface\AddOns\MageTaxi\magetaxi.lua:149: in function `MageTaxi_createGUI'
[string "MageTaxi_createGUI()"]:1: in main chunk
[C]: in function `RunScript'

Locals: i = 1
(for index) = 2
(for limit) = 7
(for step) = 1
num = 2
(*temporary) = nil
(*temporary) = nil
(*temporary) = "2"
(*temporary) = "attempt to index field '?' (a nil value)"

As far as the checkbuttons, it's only creating one and stopping (leading to the error, figured that part out). I'm looking for WHY it's not building all the buttons.