attempt to index a nil value?

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:9: attempt to index a nil value

Here is the script (It is a regular script in game.Workspace):

local ChunkSize = 144
local ChunkCounter = 0
local Chunks = {game.ServerStorage.Chunks:GetChildren()}

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

Remove the brackets on line 3

local Chunks = game.ServerStorage.Chunks:GetChildren()

What you're currently saying is get the children (which is a table), but you're storing the children in another table. Visually, this is what your problem looks like:

--Chunks table
Chunks = {
	(another table containing all the game.ServerStorage.Chunks children)
}

print(Chunks[1]) -- prints the game.ServerStorage.Chunks:GetChildren() table which is inside the Chunks table