LocalPlayers a nil value?

So, recently I have migrated my testing Level System and Experience into the ROBLOX data save scripts, however I want to keep the level system scripts for the XP bar.

However when I do so, and edit the script it says LocalPlayers is a nil value when I'm using it in a variable.

Here is the script:

local player = game.Players.LocalPlayer
Level = game.Players.LocalPlayer.Data:WaitForChild("Level")
XP = game.Players.LocalPlayer.Data:WaitForChild("XP")
XP.Changed:connect(function() XPChange(player,XP,Level) end)

function XPChange(Player,XP,Level) ------ XPChanged function
	if XP.Value >= Level.Value*150  then ----- this function occours happens if the Level's Value is greater or equal to this 150 ([Note]: Change 150 to the max XP)
		XP.Value = 0 --- Resets the XP
		Level.Value = Level.Value+ 1
	end
end

Thanks for the help!

The only way to get that error is that you are not using a localscript!