If I navigate to the OID of a Thing that no longer exists, I shouldn't get a Tag page

(Bug, Closed -> Fixed, Priority: Critical, Test Status: No automated tests yet , Reported By Bad Link: Thing 3y284oe not found, )
Summary: That is, if I navigate to, eg, "#.79s09xc9", I wind up with that as a Tag. That's both confusing and unnecessary, since it isn't a legal Tag -- names can't start with ".".
We should instead probably navigate to Space Root, and flash a "That Thing does not exist" warning.
Eric pointed this out in the context of Recent Changes -- you could get to this situation if you deleted a Published Instance, and then clicked on it from the Recent Changes page. That is being addressed elsewhere, but there are other situations that can lead to this.