messages: sender: Fail gracefully if "from" header is not a pair.

* mumi/messages.scm (sender): Fall back to "Unknown sender" if "from"
header is not a pair.

1 files changed, 4 insertions, 3 deletions

diff --git a/mumi/messages.scm b/mumi/messages.scm
index a743893..ae39b9a 100644
--- a/mumi/messages.scm
+++ b/mumi/messages.scm
@@ -85,9 +85,10 @@ yet.  Return new results alongside cached results."
   (assoc-ref (or (email-headers message) '()) key))
 
 (define (sender message)
-  (or (and=> (header message 'from) first)
-      '((name . "Unknown sender")
-        (address . "unknown"))))
+  (let ((from (header message 'from)))
+    (or (false-if-exception (and=> from first))
+        `((name . ,(or from "Unknown sender"))
+          (address . "unknown")))))
 
 (define sender-email
   (compose extract-email sender))