- [gemini] parse link even if link name is empty

sometimes you can met a link like:

=>URI<space><linebreak>

even if this  is, in my opinion,  a malformed link (there  should be a
text -the link name- after the space) parse anyway as if the link name
exists and is empty.

src/gemini/gemini-parser.lisp

@@ -71,7 +71,7 @@
 (defrule link (and link-prefix
                    link-url
                    (? (and space
-                           link-name))
+                           (? link-name)))
                    cr-lf)
   (:function (lambda (a)
                (list (first a)