why do I get a error in game but not in studio it says that line 13 cant destroy a nil?

local plr = script.Parent.Parent.Parent.Parent.Parent
local Clicked = false

script.Parent.MouseButton1Click:Connect(function()
	local Twoplayers = math.random(1,2)
	local Threeplayers = math.random(1,3)
	local Fourplayers = math.random(1,4)
	local TableOfPlayers = game.Players:GetPlayers()
	script.Parent.Parent.Parent.Enabled = false
	if Clicked == false then
		Clicked = true
		for i = 0, 5 do
			local block = game.Workspace.Blocks:FindFirstChild(plr.Name)
			block:Destroy()
			Clicked = false
		end	
	end

Error is on line 13

i think you have to put it as:

local block = game.Workspace.Blocks:FindFirstChild(tostring(plr.Name))

im not 100% sure it will work but yeah

I found the answer it was a mistake with naming the cubes. Sorry for wasting anytime and thank you for anyone that helped me! and remember to always check over your code.