Defend against empty headers.

diff --git a/mumi/messages.scm b/mumi/messages.scm
index e6edfe0..2e0f8ca 100644 (file)
--- a/mumi/messages.scm
+++ b/mumi/messages.scm
@@ -47,7 +47,7 @@
 (define-public extract-email mu-address-get-email)
 
 (define (header message key)
-  (first (assoc-ref (email-headers message) key)))
+  (and=> (assoc-ref (email-headers message) key) first))
 
 (define-public (sender message)
   (header message "from"))