Be more resilient against invalid headers in mml-generate-mime

* lisp/gnus/mml.el (mml-generate-mime): Don't bug out when called
with invalid headers (bug#55014).

diff --git a/lisp/gnus/mml.el b/lisp/gnus/mml.el
index 5a526025061a21a9d0e22623c78a8a8d069b2988..093e582ea7a888fea950b798c3b6957ebc80a770 100644 (file)
--- a/lisp/gnus/mml.el
+++ b/lisp/gnus/mml.el
@@ -500,7 +500,8 @@ type detected."
       (when (and (consp (car cont))
                 (= (length cont) 1)
                 content-type)
-       (setcdr (assq 'type (cdr (car cont))) content-type))
+        (when-let ((spec (assq 'type (cdr (car cont)))))
+         (setcdr spec content-type)))
       (when (fboundp 'libxml-parse-html-region)
        (setq cont (mapcar #'mml-expand-all-html-into-multipart-related cont)))
       (prog1