Avoid elisp crash for OpenPGP User IDs with no e-mail address

* lisp/gnus/mml-sec.el (mml-secure-check-user-id): Verify that
there is an e-mail address in the current User ID before trying
to downcase it.  (Bug#34121)

Copyright-paperwork-exempt: yes

1 files changed, 2 insertions, 0 deletions

diff --git a/lisp/gnus/mml-sec.el b/lisp/gnus/mml-sec.el
index 8c485fec376..4fca4ce67b7 100644
--- a/lisp/gnus/mml-sec.el
+++ b/lisp/gnus/mml-sec.el
@@ -658,6 +658,8 @@ The passphrase is read and cached."
     (catch 'break
       (dolist (uid uids nil)
         (if (and (stringp (epg-user-id-string uid))
+                 (car (mail-header-parse-address
+                       (epg-user-id-string uid)))
                  (equal (downcase (car (mail-header-parse-address
                                         (epg-user-id-string uid))))
                         (downcase (car (mail-header-parse-address