get-dispatch-macro-character doesn't signal errors in compiled code

[Raymond Toy]

This example is from the clisp mailing list

* (defun dispatch-macro-char-p (char rt)
  (handler-case (prog1 t 
		  (get-dispatch-macro-character char #\x rt))
    (error () nil)))
DISPATCH-MACRO-CHAR-P
* (dispatch-macro-char-p #\$ (copy-readtable nil))
NIL
* (compile 'dispatch-macro-char-p)
DISPATCH-MACRO-CHAR-P
NIL
NIL
* (dispatch-macro-char-p #\$ (copy-readtable nil))
T

I think this is because get-dispatch-macro-character is declared to be flushable. I think that's wrong since get-dispatch-macro-character is supposed to signal errors.