Datastore is returning nil...?

local Data = game:GetService("DataStoreService"):GetDataStore("Saves")
local HS = game:GetService("HttpService")

local Shirts = game.Workspace.Sir.Shirts
 
game.Players.PlayerAdded:connect(function(player)
	
	local PKey = "user_" .. player.userId
	
	
	local Stats = Instance.new("Model",player)
	Stats.Name = "UserStat"
	local SavesLists = HS:JSONDecode((Data:GetAsync(PKey)))
	
	
	local ShirtColor = Instance.new("StringValue",Stats)
	ShirtColor.Name = "ShirtColor"
	ShirtColor.Value = tostring(SavesLists[1])
	

	local ShirtType = Instance.new("StringValue",Stats)
	ShirtType.Name = "ShirtType"
	ShirtType.Value = tostring(SavesLists[2])
	
	
	if tostring(ShirtColor.Value) == "" then ShirtColor.Value = "Institutional white" end
	if tostring(ShirtType.Value) == "" then ShirtType.Value = "1" end
	
	
	for i,v in pairs(Shirts:GetChildren()) do
	for i,d in pairs(v:GetChildren()) do
	if d:IsA("BasePart") then
	if d.Parent.Name ~= "Shirt"..ShirtType then
	d.Transparency = 1
	else
	d.Transparency = 0
	end
	d.BrickColor = BrickColor.new(ShirtColor.Value)
	end
	end
	end
	
	
	function Update()
	local Table = {ShirtColor.Value,ShirtType.Value}
	local SavesList = HS:JSONEncode(Table)
	Saves:SetAsync(P, SavesList)
	end
	
	
	ShirtColor.Changed:connect(function(Val)
	Update()
	end)
	
	ShirtType.Changed:connect(function(Val)
	Update()
	end)
	

end)

Output:

Argument 1 missing or nil at line 13