Datastores not working?

I'm getting the error Players.Player.PlayerGui.ScreenGui.Dollars.TextLabel.Script:39: attempt to index local 'playerData' (a number value) online 39. Why is this?

plr = script.Parent.Parent.Parent.Parent.Parent
dollarstheyhave = 0

notLead = Instance.new('Model', plr)
notLead.Name = 'notleaderstats'
doll = Instance.new('NumberValue', notLead)
doll.Name = 'Dollars'
doll.Value = dollarstheyhave

------------------------------------------------------------------------------------
plr:WaitForChild('notleaderstats').Dollars.Changed:connect(function()
	changetext(tostring(plr.notleaderstats.Dollars.Value))
	update(plr)
end)
------------------------------------------------------------------------------------

function changetext(msg)
	script.Parent.Text = msg
end


ds = game:GetService("DataStoreService"):GetDataStore('Dollars')

function update(player)
	local playerIdentity = player.Name .. '(' .. player.userId .. ')' --Makes identity
 
	local playerKey = 'player_' .. player.userId	--Makes key
	local playerData = ds:GetAsync(playerKey)		--gets datastore 
	
	for i,v in pairs (ds:GetChildren()) do
		print(v)
	end
 
	if playerData then
		if playerData.Amount <= 0 then  --FIX THIS: ERROR SAYS ARGUMENT 2 IS MISSING OR NIL WHICH MEANS WE NEED TO FIX THE playerData.personalPlaceId PART
			playerData = nil
		end	
	end
 
	if not playerData then				
		--ADD TUTORIAL THING
 		playerData = {
			Amount = 10
		}
		ds:SetAsync(playerKey, playerData)
	end			
 
	if playerData and playerData.personalPlaceId then	
		dollarstheyhave = playerData
	end	
end