Raycasting AI freezes when gets nil value if target suddenly disappeared by whatever reason is?

Ranged AI raycasting goes nil value if target suddenly disappeared by whatever reason.

I tried to make Ranged AI by my self with some online guide and wiki.. Thought I made everything correct but single error struggling me down.

Here are my codes

function checkSight(target)
    local ray = Ray.new(rootpart.Position, (target.Position - rootpart.Position).Unit * AttackRange)
    local part,position = workspace:FindPartOnRayWithIgnoreList(ray, {script.Parent})
    if part then
        if part:IsDescendantOf(target.Parent) then
                return true
        end
    end
    return false
end

function BulletTrace()
    local Victim = nil
    for i,v in ipairs(workspace:GetChildren()) do
        local humanoid = v:FindFirstChild("Humanoid")
        local torso = v:FindFirstChild("Torso") or v:FindFirstChild("HumanoidRootPart")
        if humanoid and torso and v.Name ~= script.Parent.Name and v.Name ~= Ally1 and v.Name ~= Ally2 then
            if (rootpart.Position - torso.Position).magnitude < sight and humanoid.Health > 0 then
                Victim = torso
                Victim.Parent.PrimaryPart = Victim
            end
        end
    end
    if Victim then
        return Victim.Parent:GetPrimaryPartCFrame(),CFrame.new(Victim.Parent.Humanoid.WalkToPoint).lookVector
    end
end

function Shoot()
    local VictimPPart,AimTrack = BulletTrace()
    local VictimPPart = VictimPPart.Position -- Line 150
    local aim = VictimPPart+Vector3.new(math.random(-Accuracy*.008,Accuracy*.008),math.random(-Accuracy*.009,Accuracy*.009),math.random(-Accuracy*.1,Accuracy*.1))*(2+math.random())+AimTrack
    local OnHit,MyPosition = workspace:FindPartOnRay(Ray.new(barrel.Position,(aim - barrel.Position).Unit * (AttackRange * 2)), me)
    if VictimPPart then 

    ...

        if OnHit then -- Line 185, causing issue sometimes aswell.
        local gnomed = OnHit.Parent:findFirstChildOfClass("Humanoid")
            if gnomed then 
                gnomed:TakeDamage(damage)
            end
            else
            print("Hit failed :",me.Name)
        end

    ...

end

function Attack(target)
    if not reload then
    repeat 
        local forwardVector = (target.Position - rootpart.Position).Unit
        local upVector = Vector3.new(0,1,0)
        local rightVector = forwardVector:Cross(upVector)

        wait(FireRate)
        for i = 0, 1, 0.1 do 
            rootpart.CFrame = rootpart.CFrame:lerp(CFrame.fromMatrix(rootpart.Position, rightVector, upVector),i)
        end
        Shoot()

        if (rootpart.Position - target.Position).magnitude < RetreatMinRange then
            human.AutoRotate = false
            local c = rootpart.CFrame * CFrame.new(0,0,RetreatDistance)
            human:MoveTo(c.p)
        end

        human.AutoRotate = true
    until checkSight(target) == false or target == nil or target.Parent.Humanoid.Health < 1 -- Line 233
    else
    reloading(true)
    end
end

And the error is :

model.script:150: attempt to index nil with 'Position' Stack Begin
Stack Begin
Script 'model.script', Line 150 - function Shoot
Script 'model.script', Line 224 - function Attack
Script 'model.script', Line 106 - function pathToLocation
Script 'model.script', Line 243 - function main
Script 'model.script', Line 269
Stack End

model.script:233: attempt to index nil with 'Humanoid' Stack Begin
Stack Begin
Script 'model.script', Line 233 - function Attack
Script 'model.script', Line 106 - function pathToLocation
Script 'model.script', Line 243 - function main
Script 'model.script', Line 269
Stack End

Rarely, Line 185 'OnHit' making similar issue with Line 150 aswell. but difference is it gets nil value it self.

The error codes seems to be happen on '150' and '233' alot which seems to be relate with ray casting on BulletTrace and checkSight, but I don't know how I could fix this.

These error seems to be happen when the target suddenly died or evaded their shot with jumping down cliff or else.

Majority of bots are ok, but it happen occasionally with few of them.

doesn't these kinds of ray usually go over if there aren't any target found?

I've tried most of way I could imagine, like add some if line when it gets nil but didn't work with my tries. Now I don't get any idea how could I fix this. anyone help?