Unable to cast to dictionary?

So i'm making a fire ball and i'm scripting it so when it hits something it expands in size and then disappears. I'm using the TweenService for this and it comes back with an error saying "Unable to cast to dictionary". I then tried to use the pcall function to see if it would work but no it didn't. I don't understand, any help?

Here is my script.

game.ReplicatedStorage.Events.FireBallEvent.OnServerEvent:Connect(function(plr)
	local fire = Instance.new("Part")
	fire.Parent = workspace
	fire.Shape = "Ball"
	fire.Material = Enum.Material.Neon
	fire.CFrame = plr.Character.UpperTorso.CFrame
	fire.Size = Vector3.new(4,4,4)
	fire.CanCollide = false
	fire.BrickColor = BrickColor.new("Bright yellow")
	fire.Anchored = false
	local bv = Instance.new("BodyVelocity",fire)
	bv.Velocity = plr.Character.UpperTorso.CFrame.LookVector.Unit * 50
	bv.MaxForce = Vector3.new(math.huge,math.huge,math.huge)
	if fire.Parent == workspace then
		local tween = game:GetService("TweenService")	
		local tweeninfo = TweenInfo.new(
		1,			
		Enum.EasingStyle.Linear,
		Enum.EasingDirection.Out,
		0,
		false,
		1)
		local properties = {
		Size = Vector3.new(10,10,10)
		}		
		local create = tween:Create(tweeninfo,properties,fire)
		fire.Touched:connect(function(hit)
		create:Play()
	if hit.Parent:FindFirstChild('Humanoid') then
		local player = game.Players:GetPlayerFromCharacter(hit.Parent)
		if player then
			return nil
		else
			hit.Parent.Humanoid:TakeDamage(5)
					end
				end	
			end)
		if fire.Parent == workspace then
		wait(3)
		fire:Destroy()
		end
	end
end)