loading screen tween not working?

I am doing some test with this script from developer hub it works perfectly however when I tried to tween it only goes to haft way

output 13:31:44.726 - Players.gamingwithjbthepro.PlayerGui.LocalScript:34: invalid argument #3 (UDim2 expected, got boolean)

local ContentProvider = game:GetService("ContentProvider")
local Players = game:GetService("Players")

local localPlayer = Players.LocalPlayer
local playerGui = localPlayer:WaitForChild("PlayerGui")
local screenGui = Instance.new("ScreenGui", playerGui)

local frame = Instance.new("Frame", screenGui)
frame.Size = UDim2.new(0.5, 0, 0.1, 0)
frame.Position = UDim2.new(0.5, 0, 0.5, 0)
frame.AnchorPoint = Vector2.new(0.5, 0.5)

local bar = Instance.new("Frame", frame)
bar.Size = UDim2.new(0, 0, 1, 0)
bar.Position = UDim2.new(0, 0, 0, 0)
bar.BackgroundColor3 = Color3.new(0, 0, 1)

local puddle = game.Workspace.Puddle
local Road = game.Workspace.Road


local assets = {
    puddle,
    Road
}

wait(3)

for i = 1, #assets do
    local asset = assets[i]
    ContentProvider:PreloadAsync({asset}) -- 1 at a time, yields
    local progress = i / #assets
    bar.Size = bar.Size + bar:TweenSize(UDim2.new(progress,0,1,0),"Out","Sine",1)
end

print("loading done")

I need help with this urgently because I gonna make my own version of this