How do I "define" a variable that is already said earlier in the code?

I have this script for aiming down a scope for a shooter game. in one of the if else functions I get an error that reads: attempt to index nil with 'aimSmooth'. This issue only occurs for the second time that is stated.

Code:

RunService.RenderStepped:Connect(function()

    local rot = camera.CFrame:ToObjectSpace(lastCameraCF)
    local X,Y,Z = rot:ToOrientation()
    swayCF = swayCF:Lerp(CFrame.Angles(math.sin(X) * currentSwayAMT, math.sin(Y) * currentSwayAMT, 0), .1)
    lastCameraCF = camera.CFrame

    local humanoid = character:WaitForChild("Humanoid")

    if humanoid then
        local bobOffset = CFrame.new()

        if humanoid.MoveDirection.Magnitude > 0 then
            if humanoid.WalkSpeed == 13 then
                bobOffset = bobOffset:Lerp(CFrame.new(math.cos(tick() * 10) * .2, -humanoid.CameraOffset.Y/3, -humanoid.CameraOffset.Z/3), .1)
                end

            elseif humanoid.WalkSpeed == 20 then
                bobOffset = CFrame.new(math.cos(tick() * 18) * .3, -humanoid.CameraOffset.Y/3, -humanoid.CameraOffset.Z/3)
            end

        else
             bobOffset = bobOffset:Lerp(CFrame.new(0, -humanoid.CameraOffset.Y/3, 0), 0)
        end

        for i, v in pairs(camera:GetChildren()) do
            if v:IsA("Model") then
                v:SetPrimaryPartCFrame(camera.CFrame * swayCF * aimCF * bobOffset)
            end
        end
    end)

    if isAiming and framework.viewmodel ~= nil and framework.module.canAim then
        local offset = framework.viewmodel.AimPart.CFrame:ToObjectSpace(framework.viewmodel.PrimaryPart.CFrame)
        aimCF = aimCF:Lerp(offset, framework.module.aimSmooth)
        currentSwayAMT = aimSwayAMT
    else
        local offset = CFrame.new()
        aimCF = aimCF:Lerp(offset, framework.module.aimSmooth)
        currentSwayAMT = swayAMT
end

Line 39 is the code in question, right under the first time it was mentioned (line 35). Line 35 works just fine still.

For more info, the following code is a module script that supports this one. The code is to change the speed and smoothness of the aiming system.

local Settings = {

    canAim = true;
    aimSmooth = .07;

}

return Settings