Incorrect concatenate! definition

[jvg-upr]

concatenate! does not behave as specified in SRFI 1. It breaks if the list contains an empty list, except when it's the last element.

(concatenate `(() (1)))
;;; => (1)
(concatenate! `(() (1)))
;;; => ERROR in last-pair on line 58 of file /usr/share/chibi/srfi/1/selectors.scm: cdr: not a pair: ()