error handling in slugify

src/content.lisp

@@ -39,7 +39,11 @@
 
 (defun slugify (string)
   "Return a version of STRING suitable for use as a URL."
-  (remove-if-not #'slug-char-p (substitute-if #\- #'unicode-space-p string)))
+  (let ((slugified (remove-if-not #'slug-char-p 
+								  (substitute-if #\- #'unicode-space-p string))))
+	(if (= 0 (length slugified))
+			(error "Post title '~a' does not contain characters suitable for a slug!" string)
+			slugified)))
 
 ;; Content Types