Return a 404/410 for dead tracked links instead of redirecting to zernio.com

When a tracked DM link (my.zernio.com/r/<token>) can't find its destination, a browser is redirected to the zernio.com homepage. For platforms building on Zernio, our customers' followers then land on a brand they've never heard of. A plain 404 or 410 page would be much safer.