Why does my admin script not work?

here is the error I get.

Workspace.Script:3: bad argument #1 to 'pairs' (table expected, got nil)

And here is the script.

admins = {"amegaman"}

for i,v in pairs(isAdmin) do
	for x,c in pairs(admins) do
		if c and v == true then
			return true
		elseif c.Chatted and true then
			c.Chatted = true return
		end
	end
end

function message()
	if msg:sub(1,4) == "msg " then
		vic = msg:sub(1,9)
		m = Instance.new("Message")
		m.Parent = game.Workspace
		m.Text = (vic.Name.." "..Chatted)
	end
end