emacs-27 c156723: Fix Rmail summary display when From: header is malformed

[Eli Zaretskii]

branch: emacs-27
commit c15672376943ae6bfe05f3ab91f5b8a65a9d8d4a
Author: Eli Zaretskii <eliz@gnu.org>
Commit: Eli Zaretskii <eliz@gnu.org>

    Fix Rmail summary display when From: header is malformed
    
    * lisp/mail/rmailsum.el (rmail-header-summary): Remove newlines
    from the "From:" value, to avoid producing corrupted summary
    display.
---
 lisp/mail/rmailsum.el | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/lisp/mail/rmailsum.el b/lisp/mail/rmailsum.el
index cc55451..2eda322 100644
--- a/lisp/mail/rmailsum.el
+++ b/lisp/mail/rmailsum.el
@@ -786,6 +786,11 @@ the message being processed."
                 ;; To: =?UTF-8?Q?=C5=A0t=C4=9Bp=C3=A1n_?= 
=?UTF-8?Q?N=C4=9Bmec?=
                 ;; <stepnem@gmail.com>
                 (setq from (rfc2047-decode-string from))
+                 ;; We cannot tolerate any leftover newlines in From,
+                 ;; as that disrupts the rmail-summary display.
+                 ;; Newlines can be left in From if it was malformed,
+                 ;; e.g. had unbalanced quotes.
+                 (setq from (replace-regexp-in-string "\n+" " " from))
                 (setq len (length from))
                 (setq mch (string-match "[@%]" from))
                 (format "%25s"