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?