How can I detect a character?

This cannon script I made errors out if the player leaves while on a cannon. 13:48:00.115 - Workspace.Map.Cannon.CannonScript:19: attempt to index field 'Character' (a nil value)

local cannon = script.Parent
local click = cannon.ClickDetector
click.MouseClick:Connect(function(playerClick)
    if cannon.IsPlayerOn.Value == true then return end
    cannon.IsPlayerOn.Value = true
    local character = playerClick.Character or playerClick.CharacterAdded:Wait()
    local xrandom = math.random(-180,180)
    local yrandom = math.random(-45,0)
    cannon.MovingCannon.CannonPart:SetPrimaryPartCFrame(cannon.MovingCannon.CannonPart.PrimaryPart.CFrame * CFrame.Angles(math.rad(yrandom),0,0))
    cannon.MovingCannon:SetPrimaryPartCFrame(cannon.MovingCannon.PrimaryPart.CFrame * CFrame.Angles(math.rad(xrandom),0,0))
    if character then
        character.PrimaryPart.Anchored = true
        playerClick.Character:SetPrimaryPartCFrame((cannon.MovingCannon.CannonPart.CannonBarrel.CFrame + cannon.MovingCannon.CannonPart.CannonBarrel.CFrame.lookVector*4.5))
        playerClick.Character:WaitForChild("Humanoid").WalkSpeed = 0
        wait(2)
        if character then
            if character:FindFirstChild("HumanoidRootPart") then
                character.HumanoidRootPart.Anchored = false
                playerClick.Character:WaitForChild("Humanoid").Health = 0
                local explosion = Instance.new("Explosion", game.Workspace)
                explosion.DestroyJointRadiusPercent = 0
                explosion.BlastRadius = 0
                explosion.Position = cannon.MovingCannon.CannonPart.CannonBarrel.Position + cannon.MovingCannon.CannonPart.CannonBarrel.CFrame.LookVector*4.5
                cannon.Sound:Play()
                spawn(function()
                    character.Humanoid.Health = 0
                    character.UpperTorso.Velocity = cannon.MovingCannon.CannonPart.CannonBarrel.CFrame.LookVector * 400
                    character.UpperTorso.RotVelocity = Vector3.new(math.random(-10,10),math.random(-10,10),math.random(-10,10))
                end)
                wait(2)
                cannon.MovingCannon.CannonPart:SetPrimaryPartCFrame(cannon.MovingCannon.CannonPart.PrimaryPart.CFrame * CFrame.Angles(math.rad(-yrandom),0,0))
                cannon.MovingCannon:SetPrimaryPartCFrame(cannon.MovingCannon.PrimaryPart.CFrame * CFrame.Angles(math.rad(-xrandom),0,0))
                cannon.IsPlayerOn.Value = false
            end
        else
            print("No character detected.")
            cannon.MovingCannon.CannonPart:SetPrimaryPartCFrame(cannon.MovingCannon.CannonPart.PrimaryPart.CFrame * CFrame.Angles(math.rad(-yrandom),0,0))
            cannon.MovingCannon:SetPrimaryPartCFrame(cannon.MovingCannon.PrimaryPart.CFrame * CFrame.Angles(math.rad(-xrandom),0,0))
            cannon.IsPlayerOn.Value = false
        end
    end
end)

How can I fix this?