attempt to index nil with 'GetChildren' Line 56?

i've been trying to fix this for the past 3 days, please help

-- Vars

    local ReplicatedStorage = game:GetService("ReplicatedStorage")

    local ServerStorage = game:GetService("ServerStorage")

    local MapsFolder = ServerStorage:WaitForChild("Maps")

    local Status = ReplicatedStorage:WaitForChild("Status")

    local GameLength = 180


    -- Loop The Game If No One Wins

    while true do

        Status.Value = "2 players needed to start the game"

        repeat wait(1) until game.Players.NumPlayers >=2

        Status.Value = "Intermission"

        wait(20)

        local plrs = {}

        for i, player in pairs(game.Players:GetPlayers()) do
            if player then

                table.insert(plrs,player)-- add players to table

            end
        end
        wait(2)

        local availableMaps = MapsFolder:GetChildren()

        local ChosenMap = availableMaps[math.random(1,#availableMaps)]

        Status.Value = ChosenMap.Name.." was picked"

        local ClonedMap = ChosenMap:Clone()

        ClonedMap.Parent = workspace


        --Tp players

        local SpawnPoint = ClonedMap:FindFirstChild("SpawnPoints")

        if not SpawnPoint then
            print("Spawnpoints is not found")
        end

        local AvailableSpawnPoint = SpawnPoint:GetChildren()

        for i, player in pairs(plrs) do
            if player then
                character = player.Character

                if character then 
                    -- tp
                    character:FindFirstChild("Torso").CFrame = AvailableSpawnPoint[1]
                    table.remove(AvailableSpawnPoint,1)

                    --give a tool

                    local Sword = ServerStorage.Sword.Clone()
                    Sword.Parent = player.Backpack

                    local GameTag = Instance.new("BoolValue")
                    GameTag.Name = "GameTag"
                    GameTag.Parent = player.Character



                else
                    -- is no char

                    if not player then
                        table.remove(plrs,i)
                    end
                end
            end
        end


        Status.Value = "Starting Game"

        wait(2)
        for i = GameLength,0,-1 do

            for x, player in pairs(plrs) do
                if player then
                    character = player.Character
                    if not character then
                        -- left
                    else
                            if character:FindFirstChild("GameTag")then
                                print(player.Name.."is still in the game")
                            else
                                    -- they are deade
                                    table.remove(plrs,x)
                                    print(player.Name.."has been removed")
                            end
                    end
                end

                    table.remove(plrs,x)
                    print(player.Name.."has been removed")

            end

            Status.Value = i.." time left, and "..plrs.." Players left"

            if #plrs == 1 then
                Status.Value = plrs[1].Name.." has won the game."
                plrs[1].leaderstats.Coins.Value = plrs[1].leaderstats.Coins.Value + 200

                break

                elseif #plrs == 0 then
                    Status.Value = "Sadly, no one won"
                    break

                    elseif i == 0 then
                        Status.Value = "Time's up lads'. Good luck next time"
                    break
                end

            wait(1)
        end

        print("End of game")

        for i, player in pairs (game.Players:GetPlayers()) do
            character =  player.Character

            if not character then
                --ignore
            else 
                if character:FindFirstChild("GameTag") then
                    character.GameTag:Destroy()
                end
                if player.Backpack:FindFirstChild("Sword") then
                    player.Backpack.Sword:Destroy()
                end
                if character.Backpack:FindFirstChild("Sword") then
                    character.Sword:Destroy()
            end
        end


        player:LoadCharacter()
    end




    ClonedMap:Destroy()

    Status.Value = "Game ended"

    wait(2)
end

this script is from alvinblox, but i cant seem to find out how to fix it