Comment 1 for bug 1581204

Ideas for a fix: register-system-definition could have an unwind-protect that change-class the system to a class that reports error during definition when used. It might not be a good idea to "simply" try to un-register the system, because other systems might already have linked to that system. Maybe both can be done (?) but the system object probably shouldn't be left in a state that silently fails to fail when used even though it's actually bogus.