Saving table giving nil value when loading the data, how to fix it?

Here's my data save and load script:

local DataStoreService = game:GetService("DataStoreService");
local PD = DataStoreService:GetDataStore("PlayerData");

function SaveData(Player)
    local TableSave = {};
    TableSave.Level = Player.PlayerData.Stats.Level.Value;
    local TableItems = {};
    local ItemNumber = 0;
    for i,v in pairs(Player.PlayerData.Items:GetChildren()) do
        ItemNumber = ItemNumber + 1;
        TableItems["Item"..ItemNumber]={};
        local TI = TableItems["Item"..ItemNumber];
        TI.ItemName = v.Name;
        TI.Level = v.Level.Value;
        TI.Damage = v.Damage.Value;
    end
    table.insert(TableSave,TableItems);
    TableSave.ItemNumber = ItemNumber;
    PD:SetAsync(Player.userId,TableSave);
end

function LoadData(Player)
    local success, err = pcall(function()
        PLD = PD:GetAsync(Player.userId);
    end)
    if success then
        Player.PlayerData.Stats.Level.Value = PLD.Level;
        for i = 1,PLD.ItemNumber do
			local CurrentItem = Instance.new("Folder");
            CurrentItem.Name = PLD[1]["Item"..i].ItemName;
            local Lv = Instance.new("IntValue");
            Lv.Name = "Level";
            Lv.Value = PLD[1]["Item"..i].Level;
            Lv.Parent = CurrentItem;
            local Dm = Instance.new("IntValue");
            Dm.Name = "Damage";
            Dm.Value = PLD[1]["Item"..i].Damage;
            Dm.Parent = CurrentItem;
            CurrentItem.Parent=Player.PlayerData.Items;
        end
	else
		print("ERROR IN GET ASYNC");
    end
end

game.Players.PlayerRemoving:Connect(function(plr)
    repeat wait() until plr.PlayerData;
    SaveData(plr);
end)

game.Players.PlayerAdded:Connect(function(plr)
    repeat wait() until plr.PlayerData;
    LoadData(plr);
end)

What causes this nil problem and how to fix the problem?

GetAsync returns nil if the player does not have any data stored. You have to check if the player has any data in the first place, if not, then set their data to a default data.

Here's how it would look like:

local success, err = pcall(function()
    PLD = PD:GetAsync(Player.userId);
end)
if success then
    if not PLD then
        PLD = {
            Level = 1,
            ItemNumber = 0
        }
    end
    -- rest of your code here
end