[racket-dev] segfault with #%variable-reference

I'm not sure if #%variable-reference is supposed to be unsafe or not
(it's not mentioned in the documentation), but it looks like an
attempt to get the location of an identifier that is neither top-level
nor module-level results in a hard crash:

===
#lang racket/base

(define (go)
  (define foo 3)
  (#%variable-reference foo))

(go)