My output says "Attempted to index nil with 'WaitForChild'", what went wrong?

I'm trying to make some code to open a GUI when I press a certain key. It's going well but something went wrong. My code:

local UserInputService = game:GetService("UserInputService")
while game.Players.LocalPlayer ~= nil do
	wait(0.08)
end
local Player = game:GetService("Players").LocalPlayer
wait(1)
local PlayerGui = Player:WaitForChild("PlayerGui")

function enable()
	script.Parent.Enable.Value = 1
	while game.Lighting.Blur.Size < 10 do
		game.Lighting.Blur.Size = game.Lighting.Blur.Size + 2
		wait(0.1)
	end
end
function disable()
	script.Parent.Enabled = 0
	while game.Lighting.Blur.Size > 0 do
		game.Lighting.Blur.Size = game.Lighting.Blur.Size - 2
		wait(0.1)
	end
end

UserInputService.InputBegan:Connect(function(Input, GameProcessed)
	if (Input.KeyCode == Enum.KeyCode.P) then
		for _,v in pairs(PlayerGui:GetChildren()) do
			if (v:IsA("ScreenGui")) then 
				if script.Parent.Enable.Value == 0 then
					enable()
					v.Enabled = true
				end
				if script.Parent.Enable.Value == 1 then
					disable()
					v.Enabled = false
				end
			else
				if script.Parent.Enable.Value == 0 then
					enable()
					v.Visible = true
				end
				if script.Parent.Enable.Value == 1 then
					disable()
					v.Visible = false
				end
			end
		end
	end
end)