Avoid errors in rmailsum for messages without "From"

* lisp/mail/rmailsum.el (rmail-header-summary): Be defensive about
the presence of the "From" header.  (Bug#49770)

Copyright-paperwork-exempt: yes

diff --git a/lisp/mail/rmailsum.el b/lisp/mail/rmailsum.el
index 44cff21b062882168d86e2c6af57eaded206c589..ac933b9706d043c5f19eb7771756d2ac1e6ed0db 100644 (file)
--- a/lisp/mail/rmailsum.el
+++ b/lisp/mail/rmailsum.el
@@ -758,7 +758,8 @@ the message being processed."
                    len mch lo newline)
                ;; If there are multiple lines in FROM,
                ;; discard up to the last newline in it.
-               (while (setq newline (string-match "\n" from))
+               (while (and (stringp from)
+                           (setq newline (string-match "\n" from)))
                  (setq from (substring from (1+ newline))))
               (if (or (null from)
                       (string-match