Index: tags-html.rkt
==================================================================
--- tags-html.rkt
+++ tags-html.rkt
@@ -140,11 +140,11 @@
 ;; Provided tag functions:
 (define (html-link . args)
   `(link& [[ref ,(format "~a" (first args))]] ,@(rest args)))
 
 (define (html-url ref url)
-  (hash-set! link-urls (format "~a" ref) url))
+  (hash-set! link-urls (format "~a" ref) url) "")
 
 ;; Private use (by html-root):
 (define (decode-link-urls tx)
   (cond [(eq? (get-tag tx) 'link&)
          (let* ([url-ref (attr-ref tx 'ref)]