math.random error (interval is empty)?

I am trying to make a script that gets a random "Chunk" which is a group/model in a folder in server storage, The problem is that when it tries to pick a random "Chunk" it has this error code: Workspace.ObbyGenerator:10: bad argument #2 to 'random' (interval is empty)

Here is the code:

local ChunkSize = 144
local ChunkCounter = 0
local Chunks = {}


math.randomseed(123)

function CreateNewChunk()
    local ChunkCoordinate = ChunkSize * ChunkCounter
    local ChunkPicked = game.ServerStorage:FindFirstChild(Chunks[math.random(1, #Chunks)]):Clone()
    ChunkPicked.Parent = game.Workspace.Obby
    ChunkPicked:MoveTo(Vector3.new(ChunkCoordinate + 144, 0.5, 0))
    ChunkCounter = ChunkCounter + 1
end

local Obby = Instance.new("Model", game.Workspace)
    Obby.Name = "Obby"
local firsthundredchunks = 100
repeat
    firsthundredchunks = firsthundredchunks - 1
    ChunkCounter = ChunkCounter + 1
    wait()
until firsthundredchunks <= 0

while wait(3) do
    CreateNewChunk()
    ChunkCounter = ChunkCounter + 1
end

Thank you to anyone who can fix the problem :)