net.stun: Fix parsing of STUN packets with 0-length attributes Not sure where the '20' came from. RFC 8489 defines attributes as simple TLVs, with the type+length header being always 16 bits (4 bytes). The branch for non-zero lengths already uses the correct header size.

local xpcall = xpcall;

if select(2, xpcall(function (x) return x end, function () end,  "test")) ~= "test" then
	xpcall = require"prosody.util.compat".xpcall;
end

return {
	xpcall = xpcall;
};