"Argument 1 missing or nil" i dont know how to fix it, can someone help me?

So im trying to make a game similar to Pet Simulator X but with Missiles, and i tried making a chest opening system but the error pops out on line 51.

the error:

Argument 1 missing or nil - Client - ChestsClient:51 Stack Begin - Studio Script 'Players.UGA_BUGAGG.PlayerScripts.ChestsClient', Line 51 - function hatchChest -
Studio - ChestsClient:51 Stack End - Studio

the script:

local runService = game:GetService("RunService")
local replicatedStorage = game:GetService("ReplicatedStorage")
local players = game:GetService("Players")
local tweenService = game:GetService("TweenService")

local chests = workspace:WaitForChild("MainFolder_Workspace"):WaitForChild("Chests")
local remotes = replicatedStorage:WaitForChild("Remotes")
local pets = replicatedStorage:WaitForChild("Pets")

local player = players.LocalPlayer
local chestSystemSS = player:WaitForChild("PlayerGui"):WaitForChild("ChestSystem")
local chestViewport = chestSystemSS:WaitForChild("ChestViewport")

local function hatchChest(chestName, chosenPet)
	for _, v in pairs(player.PlayerGui:GetChildren()) do
		if v:IsA("ScreenGui") and v ~= chestSystemSS then
			v.Enabled = false
		end
	end
	chestSystemSS.Enabled = true
	for _, v in pairs(chestViewport:GetChildren()) do
		if v:IsA("Camera") or v:IsA("BasePart") or v:IsA("Model") then
			v:Destroy()
		end
	end
	chestViewport.Size = UDim2.fromScale(0, 0)
	local chestMesh = chests:FindFirstChild(chestName):Clone()
	chestMesh.Parent = chestViewport
	chestMesh.CFrame = CFrame.new(0, 0, 0)
	local camera = Instance.new("Camera")
	camera.Parent = chestViewport
	camera.CFrame = CFrame.new(0, 0, 4)
	chestViewport.CurrentCamera = camera
	tweenService:Create(chestViewport, TweenInfo.new(0.7), {Size = UDim2.new(0.604, 0,0.785, 0)}):Play()
	task.wait(0.7)
	for i = 1, 4 do
		tweenService:Create(chestViewport, TweenInfo.new(0.3, Enum.EasingStyle.Sine, Enum.EasingDirection.Out), {Rotation = 20}):Play()
		task.wait(0.3)
		tweenService:Create(chestViewport, TweenInfo.new(0.3, Enum.EasingStyle.Sine, Enum.EasingDirection.Out), {Rotation = -20}):Play()
		task.wait(0.3)
	end
	tweenService:Create(chestViewport, TweenInfo.new(0.3, Enum.EasingStyle.Sine, Enum.EasingDirection.Out), {Rotation = 0}):Play()
	task.wait(0.3)
	tweenService:Create(chestViewport, TweenInfo.new(0.7), {Size = UDim2.fromScale(0, 0)}):Play()
	task.wait (0.3)
	for _, v in pairs(chestViewport:GetChildren()) do
		if v:IsA("Camera") or v:IsA("BasePart") or v:IsA("Model") then
			v:Destroy()
		end
	end
	local petModel = pets:FindFirstChild(chosenPet.PetName):Clone()
	petModel:PivotTo(CFrame.new(0, 0, 0))
	petModel.Parent = chestViewport
	local cameraPet = Instance.new("Camera")
	cameraPet.Parent = chestViewport
	cameraPet.CFrame = CFrame.new(0, 0, -3.3) * CFrame.Angles(0, math.rad(180), 0)
	chestViewport.CurrentCamera = cameraPet
	tweenService:Create(chestViewport, TweenInfo.new(0.7), {Size = UDim2.new(0.27, 0,0.375, 0)}):Play()
	chestViewport.NameLabel.Text = chosenPet.PetName
	chestViewport.NameLabel.Visible = true
	chestViewport.RarityLabel.Text = chosenPet.Rarity
	chestViewport.RarityLabel.Visible = true
	task.wait (1.5)
	tweenService:Create(chestViewport, TweenInfo.new(0.3), {Size = UDim2.fromScale(0, 0)}):Play()
	task.wait (0.3)
	chestViewport.NameLabel.Visible = false
	chestViewport.RarityLabel.Visible = false
	for _, v in pairs(script.Parent:GetChildren()) do
		if v:IsA("ScreenGui") and v ~= chestSystemSS then
			v.Enabled = true
		end
	end
end

remotes:WaitForChild("HatchChest").OnClientEvent:Connect(hatchChest)

I believe that the chosenPet arguement you are passing has failed previously in your script, like Leamir.

You might also want to consider cloning objects on the Server Side rather than in a Local Script on the Client. This may be contributing to your issue, perhaps?