How can I prevent the part from being nil? [closed]

In the second script, I was able to detect if the object the bullet hit was related to a player's humanoid or not. This stopped the part from taking damage and being nil. Now the part is nil again because the bullet could hit the previous ray. How do I fix this?

local tool = script.Parent
local player = game:GetService("Players").LocalPlayer
local mouse = player:GetMouse()
local sound = tool:WaitForChild("Gunfire")
local sound2 = tool:WaitForChild("Reload")
local reloading = false
local contextActionService = game:GetService("ContextActionService")
local difference = 0
local replicatedstorage = game:GetService("ReplicatedStorage")
local gungui = tool:WaitForChild("GunGUI")
local bullets = tool:WaitForChild("Bullets")
local reloadtime = 3
-- Remote Events
local equipAnimation = replicatedstorage:WaitForChild("EquipAnimation")
local headshot = replicatedstorage:WaitForChild("Headshot")
local reload2 = replicatedstorage:WaitForChild("Reload")
local shootevent = replicatedstorage:WaitForChild("ShootEvent")
local unequipanimation = replicatedstorage:WaitForChild("UnequipAnimation")
-- Remote Functions
local fetchBulletsLeft = replicatedstorage:WaitForChild("FetchBulletsLeft")
-- Reloading function
    function reload()
        if bullets.Value <= 9 then
        if reloading == false then
        reloading = true
        reload2:FireServer(tool.reload)
        mouse.Icon = "http://www.roblox.com/asset?id=26573791"
        player.PlayerGui:WaitForChild("GunGUI").Bar.Bullets.Text = "R"
        sound2:Play()
        wait(reloadtime)
        bullets.Value = 10
        player.PlayerGui:WaitForChild("GunGUI").Bar.Bullets.Text = ""..bullets.Value
        mouse.Icon = "http://www.roblox.com/asset?id=42445293"
        equipAnimation:FireServer(tool.shoot)
        reloading = false
        else
            --Prevents reload spamming
            end
        end
    end
-- When the tool is equipped, the following event will run
tool.Equipped:Connect(function(mouse)
    gungui:Clone().Parent = player.PlayerGui
    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*200)
            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)

local serverStorage = game:GetService("ServerStorage")
local replicatedStorage = game:GetService("ReplicatedStorage")
local kills = "Kills"
local damage = 5
local damage2 = 10
replicatedStorage.ShootEvent.OnServerEvent:Connect(function(player,tool,position,part)
    if player.Character.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)
        --print(part.Parent.Name.." is the answer") --Optional
        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 
            print(part.Name.." is the part")
            print(part.Parent.Name.." is the parent" )
            print(part.Parent.Parent.Name.." is the ancestor" )
            local humanoid = part.Parent:FindFirstChild("Humanoid") or part.Parent.Parent:FindFirstChild("Humanoid")
            --trajectory.Name = player.Name.."'s Trajectory"

            if not humanoid then --part.Parent == game.Workspace or part.Parent.Parent.Name == game.Workspace or part.Parent.Parent.Parent.Name == game.Workspace or part.Name == trajectory.Name then

            elseif humanoid then
                if part.Name == "Head" and part.Parent:FindFirstChild("Humanoid").Health > 0 then --Extra stuff: part.ClassName == "Pants" or part.ClassName == "Accessory" or part:FindFirstAncestorOfClass("Accessory")
                -- Headshot 
                replicatedStorage.Headshot:FireClient(player)
                humanoid:TakeDamage(damage2)
                else
                    humanoid:TakeDamage(damage)
                end
            end
            wait()
            --wait(0.25)
            if trajectory then
                trajectory:Destroy()
            end
        end
    end 
end)