* lisp/emacs-lisp/debug.el (debug): Fix (bug#47588)

Don't bind `load-read-function` to nil but to its actual default value.
Actually, I'm not sure it's worth the trouble rebinding this var, but
if we do, then we should bind it to a valid value rather than to nil.

* lisp/emacs-lisp/edebug.el (edebug--eval-defun): Re-install our advice
if needed.

lisp/emacs-lisp/debug.el

@@ -213,7 +213,7 @@ the debugger will not be entered."
 	      last-input-event last-command-event last-nonmenu-event
 	      last-event-frame
 	      overriding-local-map
-	      load-read-function
+	      (load-read-function #'read)
 	      ;; If we are inside a minibuffer, allow nesting
 	      ;; so that we don't get an error from the `e' command.
 	      (enable-recursive-minibuffers