Animation unable to cash to object?

Its happening on line 12 and I dont know how to fix it i've been working on it for 2 days now does anyone know please?

local player = game:GetService("Players").LocalPlayer

repeat
    wait()
until player.Character

local char = player.Character
local hum = char:WaitForChild("Humanoid")


local animTrack = Instance.new("Animation") animTrack.AnimationId ="rbxassetid://4898878621" 
local animation = hum:LoadAnimation("rbxassetid://4898878621")

script.Parent.MouseButton1Click:Connect(function()
    animation:Play()
end)