Module:No globals

Lua error in Module:Documentation at line 144: message: type error in message cfg.container (string expected, got nil).

local mt = getmetatable(_G) or {}
function mt.__index (t, k)
	if k ~= 'arg' then
		-- perf optimization here and below: do not load Module:TNT unless there is an error
		error(require('Module:TNT').format('I18n/No globals', 'err-read', tostring(k)), 2)
	end
	return nil
end
function mt.__newindex(t, k, v)
	if k ~= 'arg' then
		error(require('Module:TNT').format('I18n/No globals', 'err-write', tostring(k)), 2)
	end
	rawset(t, k, v)
end
setmetatable(_G, mt)