Can anyone help with this roblox gun script for the crossbow by roblox? [SOLVED]

It says that in line 128 attempt to index nil with "FindFirstChild". The gun works in the basplates but I put it into my game and it does not seem to work. The script is too long but in the baseplate you can find it in the toolbox its by Roblox and its their premade crossbow. Have a look at line 128 and see if you can help me solve this error please ty. Here is only part of the script as it is 900+ characters long

local RunService = game:GetService("RunService")
local Players = game:GetService("Players")

local IsServer = RunService:IsServer()

local WeaponsSystemFolder = script.Parent.Parent
local AnimationsFolder = WeaponsSystemFolder:WaitForChild("Assets"):WaitForChild("Animations")

local localRandom = Random.new()

local BaseWeapon = {}
BaseWeapon.__index = BaseWeapon

BaseWeapon.CanAimDownSights = false
BaseWeapon.CanBeReloaded = false
BaseWeapon.CanBeFired = false
BaseWeapon.CanHit = false

function BaseWeapon.new(weaponsSystem, instance)
	assert(instance, "BaseWeapon.new() requires a valid Instance to be attached to.")

	local self = setmetatable({}, BaseWeapon)
	self.connections = {}
	self.descendants = {}
	self.descendantsRegistered = false
	self.optionalDescendantNames = {}
	self.weaponsSystem = weaponsSystem
	self.instance = instance
	self.animController = nil
	self.player = nil
	self.enabled = false
	self.equipped = false
	self.activated = false
	self.nextShotId = 1
	self.activeRenderStepName = nil
	self.curReloadSound = nil

	self.animTracks = {}
	self.sounds = {}
	self.configValues = {}
	self.trackedConfigurations = {}

	self.ammoInWeaponValue = nil

	self.reloading = false
	self.canReload = true

	self:registerDescendants()
	self.connections.descendantAdded = self.instance.DescendantAdded:Connect(function(descendant)
		self:onDescendantAdded(descendant)
	end)

	return self
end

function BaseWeapon:doInitialSetup()
	local selfClass = getmetatable(self)
	self.instanceIsTool = self.instance:IsA("Tool")

	-- Set up child added/removed
	self.connections.childAdded = self.instance.ChildAdded:Connect(function(child)
		self:onChildAdded(child)
	end)
	self.connections.childRemoved = self.instance.ChildRemoved:Connect(function(child)
		self:onChildRemoved(child)
	end)
	for _, child in pairs(self.instance:GetChildren()) do
		self:onChildAdded(child)
	end

	-- Initialize self.ammoInWeaponValue
	if selfClass.CanBeReloaded then
		if IsServer then
			self.ammoInWeaponValue = self.instance:FindFirstChild("CurrentAmmo")
			if not self.ammoInWeaponValue then
				self.ammoInWeaponValue = Instance.new("IntValue")
				self.ammoInWeaponValue.Name = "CurrentAmmo"
				self.ammoInWeaponValue.Value = 0
				self.ammoInWeaponValue.Parent = self.instance
			end
			self.ammoInWeaponValue.Value = self:getConfigValue("AmmoCapacity", 30)
		else
			self.ammoInWeaponValue = self.instance:WaitForChild("CurrentAmmo")
		end
	end

	self.connections.ancestryChanged = self.instance.AncestryChanged:Connect(function() self:onAncestryChanged() end)
	self:onAncestryChanged()

	-- Set up equipped/unequipped and activated/deactivated
	if self.instanceIsTool then
		self.connections.equipped = self.instance.Equipped:Connect(function()
			if IsServer or (Players.LocalPlayer and (self.instance:IsDescendantOf(Players.LocalPlayer.Backpack) or self.instance:IsDescendantOf(Players.LocalPlayer.Character))) then
				self:setEquipped(true)
				if self:getAmmoInWeapon() <= 0 then
					-- Have to wait a frame, otherwise the reload animation will not play
					coroutine.wrap(function()
						wait()
						self:reload()
					end)()
				end
			end
		end)
		self.connections.unequipped = self.instance.Unequipped:Connect(function()
			if IsServer or (Players.LocalPlayer and (self.instance:IsDescendantOf(Players.LocalPlayer.Backpack) or self.instance:IsDescendantOf(Players.LocalPlayer.Character))) then
				self:setEquipped(false)
				if self.reloading then
					self:cancelReload()
				end
			end
		end)
		if self.instance:IsDescendantOf(workspace) and self.player then
			self:setEquipped(true)
		end

		self.connections.activated = self.instance.Activated:Connect(function()
			self:setActivated(true)
		end)
		self.connections.deactivated = self.instance.Deactivated:Connect(function()
			self:setActivated(false)
		end)

		-- Weld handle to weapon primary part
		if IsServer then
			self.handle = self.instance:FindFirstChild("Handle")

			local model = self.instance:FindFirstChildOfClass("Model")
			local handleAttachment = model:FindFirstChild("HandleAttachment", true)

			if self.handle and handleAttachment then
				local handleOffset = model.PrimaryPart.CFrame:toObjectSpace(handleAttachment.WorldCFrame)

				local weld = Instance.new("Weld")
				weld.Name = "HandleWeld"
				weld.Part0 = self.handle
				weld.Part1 = model.PrimaryPart
				weld.C0 = CFrame.new()
				weld.C1 = handleOffset
				weld.Parent = self.handle

				self.handle.Anchored = false
				model.PrimaryPart.Anchored = false
			end
		end
	end
end