How do I make a global leaderboard?

Hello,

I am making a global leaderboard for my game that displays the top 50 players with the most "LadderPoints" (player.leaderstats.LadderPoints).

I already have a script, but there is an error on line 41: Attempt to concatenate nil with string. Here is the script (I put the whole thing incase you need to see the rest):

local sg = script.Parent
local sample = script:WaitForChild("Sample")
local sf = sg:WaitForChild("ScrollingFrame")
local ui = sf:WaitForChild("UI")

local dataStoreService = game:GetService("DataStoreService")
local dataStore = dataStoreService:GetOrderedDataStore("LadderData")

wait(5)
while true do
	for i, plr in pairs(game.Players:GetChildren()) do
		if plr.UserId > 0 then
			local w = plr.leaderstats.LadderPoints.Value
			if w then
				pcall(function()
					dataStore:UpdateAsync(plr.UserId,function(oldVal)
						return tonumber(w)
					end)
				end)
			end
		end
	end

	local smallestFirst = true
	local numberToShow = 50
	local minValue = 1
	local maxValue = 99999
	local pages = dataStore:GetSortedAsync(smallestFirst, numberToShow, minValue, maxValue)
	
	local top = pages:GetCurrentPage()
	
	local data = {}
	for a,b in ipairs(top) do
		local userid = b.Key
	    local points = b.Value
	    local username = "[Failed To Load]"
	    local s,e = pcall(function()
	    	username = game.Players:GetNameFromUserIdAsync(userid)
		end)
		if not s then
			warn("Error getting name for "..userid..". Error: "..e)
		end
		local image = game.Players:GetUserThumbnailAsync(userid, Enum.ThumbnailType.HeadShot, Enum.ThumbnailSize.Size150x150)
      
       table.insert(data,{username,points,image})
	end
	
	ui.Parent = script
	sf:ClearAllChildren()
	ui.Parent = sf
	for number,d in pairs(data) do
		local name = d[1]
		local val = d[2]
		local image = d[3]
		local color = Color3.new(1,1,1)
		if number == 1 then
			color = Color3.new(1,1,0)
		elseif number == 2 then
			color = Color3.new(0.9,0.9,0.9)
		elseif number == 3 then
			color = Color3.fromRGB(166, 112, 0)
		end
		local new = sample:Clone()
		new.Name = name--Set name for better recognition and debugging
        new.LayoutOrder = tonumber(number)
		new.Image.Image = image--Set the image
		new.Image.Place.Text = number--Set the place
		new.Image.Place.TextColor3 = color--Set the place color (Gold = 1st)
		new.PName.Text = name--Set the username
		new.Value.Text = val--Set the amount of points
		new.Value.TextColor3 = color--Set the place color (Gold = 1st)
		new.PName.TextColor3 = color--Set the place color (Gold = 1st)
		new.Parent = sf--Parent to scrolling frame
	end
	wait()
	sf.CanvasSize = UDim2.new(0,0,0,ui.AbsoluteContentSize.Y)
	wait(5)
end

Thank you so much!!!