Why is this outputting table expected got nil?

I'm playing around with Datastores and the following code works fine but after the first attempt it errors and says line 13 bad argument #1 to 'pairs' (table expected, got nil).

It works perfectly fine and it updated the data but when I leave and come back for the 2nd time it errors with that. When I tried to print data.stats it gave me a nil value??

local DS = game:GetService('DataStoreService'):GetDataStore('7')

local data
local key = '1'

local success, ret = pcall(function()
    data = DS:GetAsync(key) 
end)

if data then
    local stats = data.stats

    for k, v in pairs(stats) do
        print(k,v)
    end

    wait(1)

    DS:UpdateAsync(key, function(prev)
        stats.gold = not stats.gold
        return stats
    end)

    wait(1)

    for k, v in pairs(stats) do
        print(k,v)
    end
elseif not data then
    DS:SetAsync(key, {
        stats = {
            armor = true;
            gold = false;
            silver = false;
            wood = false;
        };
    })  
else
    error(ret)
end