Tried to make random map system.but an error invalid argument #2 to 'random' (interval is empty)?

Server script (in serverscriptservice):

local lobby_Duration = 10
local round_Duration = 10
local maps = game:GetService('ReplicatedStorage'):WaitForChild('Map'):GetChildren()
local timerval = game.ReplicatedStorage:WaitForChild("TimerValue")

local function RTimer ()
	while wait() do
		for l = lobby_Duration, 0, -1 do
			timerval.Value = 'Intermission: '..l
			wait(1)

			if l == 0 then
				local map = maps[math.random(1, #maps)] -- this is the problem
				timerval.Value = 'Teleporting players to '..map.Name 
				wait(1)
				map.Parent = workspace

				local players = game.Players:GetChildren()

				for i = 1, #players do
					players[i].Character:MoveTo(Vector3.new(-122.5, 55.5, -41.5))
				end

				wait(1)

				for g = round_Duration,0, -1 do
					timerval.Value = 'Round '..g..' seconds left'
					wait(1)

					if g == 0 then
						timerval.Value = 'Round over'
						wait(2)
						timerval.Value = 'Teleporting players to lobby'
						wait(1)
						for i = 1, #players do
							players[i].Character:MoveTo(Vector3.new(-122.5, 55.5, 32.5))
						end

						map.Parent = maps
						wait(1)
						-- repeat again
					end
				end
			end
		end
	end
end

spawn(RTimer)

try debugging by printing the "#maps" it might be because the variable maps is nil(the defined location doesn't exist) for now try that out.