ServerScriptService.MainHandler:16: attempt to index nil with 'UserId' How to fix?

So I was just following a tutorial on trello bans when this error pops up. How do we fix this?

REMINDER: I tried to find a solution for about half an hour stop commenting that downvote link...

##MainHandler Below

--Lodok3YT
--Trello Ban Script
local BoardName = "Build World Bans" --For me its Islanders
local NameOfList = "Exploiter Bans" --ie BanID or BanList

local function OnPlayerAdded(player)
	local TrelloModule = require(game.ServerStorage.Trello.Main)
	local YourBoard = TrelloModule:GetBoardByName(BoardName)
	CheckIfBanned(player,YourBoard:GetListByName(NameOfList))
end

function CheckIfBanned(player,list)
	for index, value in pairs(list:GetCards()) do --// getting cards of banned
		local cardData = value:GetData()
		if tonumber(cardData.name) == player.UserId then
			player:Kick(cardData.desc or "unspecified reason") --// if desc, then put it, else ti will put "unspecified reason"
			return true
		end
	end
	return false	
end

game:GetService("Players").PlayerAdded:Connect(OnPlayerAdded())