What do I replace Parent with to prevent roblox studio from thinking it is nil?

For my gun, I put in a trajectory block with hit.Parent but there is an error around line 35.

FYI the script is in ServerScriptService.

Error: ServerScriptService.MainScript:35: attempt to index field 'Parent' (a nil value)

The part being referred is the object being hit by the gun.

Also, I got the suggestion that :FindPartOnRay() can return nil parts but idk how to recode anything

Part of the Code:

local serverStorage = game:GetService("ServerStorage")
local replicatedStorage = game:GetService("ReplicatedStorage")
local kills = "Kills"
local damage = 10
replicatedStorage.ShootEvent.OnServerEvent:Connect(function(player,tool,position,part)
	if game.Workspace[player.Name].Humanoid.Health <= 0 then
		-- Nothing Happens
	else
		local distance = (tool.Handle.CFrame.p - position).magnitude
		if game.Workspace:FindFirstChild(player.Name.."'s Trajectory") then 
			game.Workspace:FindFirstChild(player.Name.."'s Trajectory"):Destroy()
		end
		local trajectory = Instance.new("Part",game.Workspace)
		local smoke = serverStorage.SmokeParticle:Clone()
		smoke.Parent = tool.Handle
		trajectory.BrickColor = BrickColor.new("Dark blue")
		trajectory.Material = "SmoothPlastic"
		trajectory.Name = player.Name.."'s Trajectory"
		trajectory.Transparency = 0.5
		trajectory.Anchored = true
		trajectory.Locked = true
		trajectory.CanCollide = false
		trajectory.Size = Vector3.new(0.3,0.3,distance)
		for i = 0, distance,6 do
			trajectory.CFrame = CFrame.new(tool.Handle.CFrame.p,position) * CFrame.new(0,0,-distance / 2)
			wait(0.0001)
		end
		smoke:Destroy()
		if part then 
			if part.Name == "Head" or part:IsA("Hat") and part.Parent:FindFirstChild("Humanoid").Health > 0 then
				-- Headshot
				replicatedStorage.Headshot:FireClient(player)
				damage= 20
			end
			local humanoid = part.Parent:FindFirstChild("Humanoid")
			if not humanoid then
				humanoid = part.Parent.Parent:FindFirstChild("Humanoid")
			else
				humanoid:TakeDamage(damage)
				--if humanoid.Health == 0 then
					--player.leaderstats[kills].Value = player.leaderstats[kills].Value + 1
				--end
			end
			wait(0.25)
			if trajectory then
				trajectory:Destroy()
			end
		end
	end	
end)

Also my local script inside gun in workspace (with fireEvent)

tool.Equipped:Connect(function(mouse)
	gungui:Clone().Parent = player.PlayerGui
	findBodyType()
	equipAnimation:FireServer(tool.shoot)
	mouse.Icon = "http://www.roblox.com/asset?id=42445293"
	mouse.Button1Down:Connect(function()
		if bullets.Value <=0 or reloading == true then
			-- Don't Do Anything
		else
			local head = game.Workspace[player.Name].Head.CFrame.lookVector
			local mouse = CFrame.new(game.Workspace[player.Name].Head.Position,mouse.Hit.p).lookVector
			difference = (head-mouse)
			local ray = Ray.new(tool.Handle.CFrame.p,(player:GetMouse().Hit.p - tool.Handle.CFrame.p).unit*300)
			local part,position = game.Workspace:FindPartOnRay(ray,player.Character,false,true)
			
			if difference.magnitude < 1.33 then
				sound:Play()
				shootevent:FireServer(tool,position,part)
				bullets.Value = bullets.Value - 1
			end
		end
	end)