attempt to concatenate nil with value string ??? script error

I am making a map voting script for my GUI and when I go to run the script I get this output:

01:22:09.428 - ServerScriptService.Server:104: attempt to concatenate nil with string

The error is happening on line 104:

--Assets--
local rep = game.ReplicatedStorage
local assets = rep.Assets

--Maps--
local maps = assets.Maps

--Signals--
local signals = assets.Signals
local event = signals.Event
local fevent = signals.FEvent

--Static Variables--
local mapVotes = {}

--Game Variables--
local Game = game.StarterGui.Game
local stats = Game.Stats
local settings = {
    mapVoteTime=15;
    MapVoteDelay=3;
    playersRequired=1;

}

--Primary Events--

--[[
    ARRAY = MapVotes
        MapArray
            id
            mapName
            players
                player=userId
--]]

event.OnServerEvent:connect(function(player, variables)
    if variables.reason == "voteOnMap" then
        --First check if player already voted on a map, if so then change map
        for a,b in pairs(mapVotes)do
            for d,c in pairs(b.players)do
                if c.player == player.UserId then
                    table.remove(b.players, d)
                    break
                end
            end
        end
        --Add player to the map votes
        for a,b in pairs(mapVotes)do
            if b.id == variables.itemNum then
                table.insert(b.players, {player=player.UserId})         
            end 
        end
        elseif variables.reason == "removeFromVote" then
                    for a,b in pairs(mapVotes)do
            for d,c in pairs(b.players)do
                if c.player == player.UserId then
                    table.remove(b.players, d)
                    break
                end
            end
        end
    end
end)

function getMap()
    local RandomMap = maps:GetChildren()[math.random(1,#maps:GetChildren())]
    for a,b in pairs(mapVotes) do
        if b.mapName == RandomMap.Name then
            return getMap()
        end
    end
end

while wait() do
    if #game.Players:GetPlayers() < settings.playersRequired then
        local playersNeeded = settings.playersRequired-#game.Players:GetPlayers()
        stats.Status.Value = playersNeeded.." "..((playersNeeded==1 and "Player")or "Players").."need to play!"
    else
        --assign maps
        mapVotes={}
        for a,b in pairs(Game.Special.VotingGUIs.ScreenGUI:GetChildren()) do
            table.insert(mapVotes, {id=tonumber(b.Name:match("%d+")); mapName=getMap(); players={};})
        end

        --Fire clients, start sending in votes.
        event:FireAllClients({reason="startVoting"})

        --Do main loop
        local start = tick()
        while wait() do
            if tick()-start >=settings.mapVoteTime then break end
            local secondsLeft = math.floor(settings.mapVoteTime-(tick()-start))
            stats.Status.Value = secondsLeft.." "..((secondsLeft==1 and "Second ")or "Seconds ").."Left to Vote"
            for a,b in pairs(Game.Special.VotingGUIs.ScreenGUI:GetChildren()) do
                local playersVoting, mName
                for d,c in pairs(mapVotes) do
                    if c.id == tonumber(b.Name:match("%d+")) then
                        playersVoting=#c.players
                        mName=c.mapName
                        break
                    end
                end
                b.sGui.Title.Text = mName.." - "..playersVoting.." "..((playersVoting==1 and "Voter")or "Voters")
            end
        end

        --Get winner
        table.sort(mapVotes, function(a,b) return #a.players>b.players end)

        for a,b in pairs(Game.Special.VotingGUIs.ScreenGUI:GetChildren()) do
            if tonumber(b.Name:match("%d+")) == mapVotes[1].id then
                b.sGui.Title.Text = "Winner!"
                stats.Status.Value = mapVotes[1].mapName.." was chosen!"
            else
                b.sGui.Title.Text = "Lost Vote"

                wait(settings.mapVoteDelay)
            end
        end
    end
end

if anyone knows the problem and how to fix it please tell me. I've tried everything I knew for the past 3 hours and I can't seem to get it to work.

And b = VotingGUI and the ScreenGUI holds all of those down to the text so it looks like this:

VotingGUI>sGUI>Title (which is a TextLabel renamed as "Title")

EDIT: added the local script that goes along with the server script:

--Player--
local player = game.Players.LocalPlayer
local char = player.Character or player.CharacterAdded:wait()
local gui = player:WaitForChild("PlayerGui")
local ui= gui:WaitForChild("ui")

--Assets--
local rep = game.ReplicatedStorage
local assets = rep.Assets

--Maps--
local maps = assets.Maps

--Signals--
local signals = assets.Signals
local event = signals.Event
local fevent = signals.FEvent

--Game Variables--
local Game = game.StarterGui.Game
local stats = Game.Stats

--Static Variables--
local vars = {
    currentVote=nil;
    services={};
}

--Primary Events--
event.OnClientEvent:connect(function(variables)
    if variables.reason == "startVoting" then
        table.insert(vars.services, game:GetService("RunService").RenderStepped:connect(function()
            local ray = Ray.new(char.PrimaryPart.CFrame.p, Vector3.new(0.-1000.0))
            local object = workspace:findPartOnRay(ray, char, false, false)
            if object and object.Name:match("VotingButton") then
                local votingGUINum = tonumber(object.Name:match("%d+"))
                if vars.currentVote==nil then
                    vars.currentVote = votingGUINum
                    event:FireServer({reason="voteOnMap"; itemNum=votingGUINum;})
                elseif vars.currentVote~=votingGUINum then
                    vars.currentVote = votingGUINum
                    event:FireServer({reason="voteOnMap"; itemNum=votingGUINum;})
                end
            elseif vars.currentVote~=nil then
                vars.currentVote=nil
                event:FireServer({reason="removeFromVote"})
            end
        end))
    elseif variables.reason == "endVoting" then
        for a,b in pairs(vars.services) do
            b:disconnect()
        end
        vars.services= {}
    end
end)

--Initiate Title Updater
game:GetService("RunService").RenderStepped:connect(function()
    ui:WaitForChild("Title").Text = game.StarterGui.Game.Stats.Status.Value
end)