Fix for ticket 2513: "Can't linkify" error when some links are shortened

Fix for ticket 2513: "Can't linkify" error when some links are shortened

When bogus SSL sites etc were hit through a shortening redirect, sometimes link resolution kinda blew up and the user would get a "Can't linkify" error, aborting their post.
Now catching this case and just passing through the URL without attempting to resolve it. Could benefit from an overall scrubbing of the freaky link/attachment code though...! :)

http://status.net/open-source/issues/2513