If you delete a Model that has Instances, the Space won't load any more

(Bug, Closed -> Fixed, Priority: Critical, Test Status: No automated tests yet , Reported By Bad Link: Thing 3y284oe not found, )
Internals
Summary: Almost the definition of a P1 bug: if you delete a Model that has Instances, things start to act a bit wonky. But once the Space passivates, you can't reload it -- it crashes on reload.