Error with my math.random script?

This script contains 2 functions, parts that run my game. I get an error Players.Player2.Backpack.LocalScript:20: bad argument #2 to 'random' (interval is empty) when it's time to choose the map. Any ideas why?

local player = game.Players.LocalPlayer
local messagegui = player.PlayerGui:WaitForChild("Messages")
local messageline = messagegui:WaitForChild("MessageLine")

repeat wait() until player and messageline and messagegui

function CheckPlayers()
    if game.Players.NumPlayers >= 2 then
        messageline.Text = "Game about to start."
    else
        messageline.Text = "Wait for 2 or more players."
    end
end

function ChooseMap()
    local maps = {}
    local findmaps = game.ReplicatedStorage:WaitForChild("Maps")
    for i,v in pairs(findmaps:GetChildren()) do
        table.insert(maps, v)
    end
    local chosenmap = maps[math.random(1, #maps)]
    chosenmap.Parent = workspace
end

while wait(1) do
	repeat CheckPlayers()
	until game.Players.NumPlayers >= 2
    wait(3)
    messageline.Text = "Choosing map."
    ChooseMap()
	wait(2)
end

Definition of Your Error

You error means that there was no positive difference between your arguments with the math.random function. What I mean by that is if you have math.random(1,1) then there's no positive difference.. same goes for math.random(5,2).

The math.random function has to have a positive difference between the arguments.. like so; math.random(1,4).

Why You Got This Error

You're using math.random(1,#maps) on line 20.. but there is only 1 index in your table. So you're essentially saying math.random(1,1) - which has no positive difference.

How To Fix

You need to pack every child of maps into the table, rather than just 'maps'. Then there will be a positve difference!

Code

local player = game.Players.LocalPlayer
local messagegui = player.PlayerGui:WaitForChild("Messages")
local messageline = messagegui:WaitForChild("MessageLine")

repeat wait() until player and messageline and messagegui

function CheckPlayers()
	if game.Players.NumPlayers >= 2 then
		messageline.Text = "Game about to start."
	else
		messageline.Text = "Wait for 2 or more players."
	end
end

function ChooseMap()
	local maps = {}
	local findmaps = game.ServerStorage:FindFirstChild("Maps")
	--Insert all the children
	for i,v in pairs(findmaps:GetChildren()) do
		table.insert(maps, v)
	end
	--Now you can index it randomely
	 local chosenmap = maps[math.random(1, #maps)]
	chosenmap.Parent = workspace
end

while wait(1) do
	CheckPlayers()
	wait(5)
	messageline.Text = "Choosing map."
	ChooseMap()
end

While Goul's script should work, you're trying to access ServerStorage from a LocalScript. You need to move your Maps model/folder to a place that's readable by a LocalScript, such as ReplicatedStorage.

This is becuase ROBLOX can't access the ServerStorage and ServerScriptService from a LocalScript as LocalScripts run on the client and can't read server items.

So, once you've moved your Maps model/folder to ReplicatedStorage, just use Goul's script but change ServerStorage to ReplicatedStorage on line 17:

local player = game.Players.LocalPlayer
local messagegui = player.PlayerGui:WaitForChild("Messages")
local messageline = messagegui:WaitForChild("MessageLine")

repeat wait() until player and messageline and messagegui

function CheckPlayers()
    if game.Players.NumPlayers >= 2 then
        messageline.Text = "Game about to start."
    else
        messageline.Text = "Wait for 2 or more players."
    end
end

function ChooseMap()
    local maps = {}
    local findmaps = game.ReplicatedStorage:WaitForChild("Maps") --Still using WaitForChild, in case it doesn't appear automatically.
    --Insert all the children
    for i,v in pairs(findmaps:GetChildren()) do
        table.insert(maps, v)
    end
    --Now you can index it randomely
     local chosenmap = maps[math.random(1, #maps)]
    chosenmap.Parent = workspace
end

while wait(1) do
    CheckPlayers()
    wait(5)
    messageline.Text = "Choosing map."
    ChooseMap()
end