Error 'invalid argument #1 to 'len' (string expected, got nil)', any help? [SOLVED]

Hello, and thank you for reading! This is our client:

Client:

local player = game.Players.LocalPlayer
local CreateDialogEvent = game.ReplicatedStorage.CreateDialogEvent
local DialogFrame = player.PlayerGui.DialogGUI:WaitForChild("DialogFrame")
local DialogGUI = DialogFrame.Parent
local DialogText = DialogFrame:WaitForChild("DialogText")
local OriginalSound = script:WaitForChild("Talk")
local TEXT_INTERVAL = 0.075

local function playSound(soundID)
    local Sound = OriginalSound:Clone()
    Sound:Destroy()
end

local function Talk(Text)
    for i = 1, string.len(Text) do
        DialogText.Text = string.sub(Text,1,i)
        playSound()
        if string.sub(Text,i,i) == "." or string.sub(Text,i,i) == "!" or string.sub(Text,i,i) == "?" then
            wait(.5)
        elseif string.sub(Text,i,i) == "," then
            wait(.1)
        else
            wait(TEXT_INTERVAL)
        end
    end
end

CreateDialogEvent.OnClientEvent:Connect(function(imageID,Text)
    if not player:FindFirstChild("secretEnding") then
        DialogFrame.DialogImage.Image = imageID
        DialogText = ""
        DialogGUI.Enabled = true
        Talk(Text)
    end
end)

It is located in StarterCharacterScripts.

Now, I understand this error: Text is nil, as it doesnt exist, BUT, I have no other way to access it! There is a RemoteEvent inside ReplicatedStorage called CreateDialogEvent.

Server:

local Sound = script:WaitForChild("Talk")
local TEXT_INTERVAL = 0.03
local CreateDialogEvent = game.ReplicatedStorage.CreateDialogEvent

local randomPlayerName
local randomPlayerID

local function getPlayerImage(playerID)
    local content,isReady = game:GetService("Players"):GetUserThumbnailAsync(playerID,Enum.ThumbnailType.HeadShot, Enum.ThumbnailSize.Size420x420)
    return content
end

local function getRandomPlayers()
    local Players = game.Players:GetPlayers()
    local number = math.random(1,#Players)
    local randomPlayer = Players[number]
    randomPlayerName = randomPlayer.Name
    randomPlayerID = randomPlayer.UserId
end

local function challengingExample()
    local Cab_Image = "rbxassetid://6927695957"
    CreateDialogEvent:FireAllClients(Cab_Image,"Dialog")
    wait(5)
    getRandomPlayers()
    CreateDialogEvent:FireAllClients(getPlayerImage(randomPlayerID,"Dialog 2"))
end

challengingExample()

-- Ignore the rest, I used this in the past but its here just incase.
--Talk("Loading...")
--wait(10)
--Talk("Urghh...")
--wait(6)
--Talk("Where are we?")
--wait(8)
--Talk("CAB!!!")
--wait(4)
--Talk("...")
--wait(4)
--Talk("We have to find help!")

So, that about wraps things up.

Thank you for reading, and, as always, any further questions can be answered politely!