scheme crash with (custom) renumber refdes hook

Crash when copying a component with a custom scheme hook loaded. (The hook is to un-number the named component you copy).

Hook is loaded from /home/pcjc2/.gEDA/gschemrc with:

(load-from-path "/home/pcjc2/.gEDA/unnumber-refdes.scm")
(add-hook! copy-component-hook unnumber-refdes)

Output:

gschem
WARNING: (gschem keymap): imported module (srfi srfi-69) overrides core binding `make-hash-table'
WARNING: (gschem keymap): imported module (srfi srfi-69) overrides core binding `hash-table?'
Backtrace:
In unknown file:
   ?: 0* [#<procedure #f (lst)> (# # #)]
In /home/pcjc2/geda/share/gEDA/scheme/gschem/deprecated.scm:
 267: 1* (if (not (hook-empty? tgt-hook)) (for-each (lambda (obj) (if # #)) lst))
 268: 2 [for-each #<procedure #f (obj)> (# # #)]
In unknown file:
   ?: 3* [#<procedure #f (obj)> #<geda-object 0x190b0b0>]
In /home/pcjc2/geda/share/gEDA/scheme/gschem/deprecated.scm:
 270: 4* (if (filter? obj) (run-hook tgt-hook (append! # #)))
 271: 5 [run-hook #<hook 1 7f4f357615d0 unnumber-refdes> (# # # #)]
In unknown file:
   ?: 6* [unnumber-refdes (# # # #)]
   ?: 7* (letrec (# #) (for-each # attribs))
In /home/pcjc2/.gEDA/unnumber-refdes.scm:
  34: 8 [for-each #<procedure #f (attrib)> (# # # #)]
In unknown file:
   ?: 9* [#<procedure #f (attrib)> #<geda-object 0x18d8eb0>]
In /home/pcjc2/.gEDA/unnumber-refdes.scm:
  36: 10* (let* (# # #) (if # #))
  39: 11 (if (string=? name "refdes") (set-attribute-value! attrib #))
In /home/pcjc2/geda/share/gEDA/scheme/gschem/deprecated.scm:
    ...
 133: 12 (let ((params #) (name-value #)) (list-set! params 3 ...) ...)
 135: 13* [list-set! ((56200 . 54300) lower-left 0 ...) 3 ...
 135: 14* [simple-format {"~A=~A"} "refdes" "CONN?"]

/home/pcjc2/geda/share/gEDA/scheme/gschem/deprecated.scm:135:25: In procedure simple-format in expression (simple-format "~A=~A" (car name-value) ...):
/home/pcjc2/geda/share/gEDA/scheme/gschem/deprecated.scm:135:25: Wrong type argument in position 1: "~A=~A"