Why does this script crash my game?

Trying to make a shop script but it crashes my game when i buy it plz help

--Judgmentum

local illumina = script.Parent:WaitForChild("Illumina")
local units = game.Players.LocalPlayer:WaitForChild("leaderstats").Units

function buySword(swordName, price, button)
    if units.Value >= price then
        units.Value = units.Value - price
        local weapon = game.ReplicatedStorage.Weapons:FindFirstChild(swordName)
        if weapon then
            local new = weapon:Clone()
            new.Parent = game.Players.LocalPlayer.Backpack
            new.Parent = game.Players.LocalPlayer.StarterGear
            print("Purchase successful! Bought " .. swordName .. " for " .. price .. " units.")
        else
            print("ERROR: SWORD NOT FOUND, LINE 9 OF SCRIPT 'ShopBuy' IN MAIN > SHOPBUTTON > SHOPFRAME > SHOPBUY")
            return false
        end
        button.Text = "Purchased."
        wait(2)
        button.Text = swordName
    end
end

illumina.MouseButton1Click:connect(function() buySword("Illumina", 1000, illumina) end)