bug#69712: Package author/maintainer printing fix

[Juri Linkov]

There are many packages with non-dot author/maintainer format that fail with

Debugger entered--Lisp error: (wrong-type-argument listp "XXIV")
  car("XXIV")
  package--print-email-button("XXIV")
  describe-package-1(#s(package-desc :name chaos-mode ((:authors ("XXIV")) 
(:maintainers ("XXIV")) (:maintainer "XXIV"))))
  describe-package(#s(package-desc :name chaos-mode ((:authors ("XXIV")) 
(:maintainers ("XXIV")) (:maintainer "XXIV"))))
  package-menu-describe-package(#<marker (moves after insertion) at 67389 in 
*Packages*>)
  button-activate(#<marker (moves after insertion) at 67389 in *Packages*> nil)
  push-button(67389)
  funcall-interactively(push-button 67389)
  command-execute(push-button)

Here is the fix:

diff --git a/lisp/emacs-lisp/package.el b/lisp/emacs-lisp/package.el
index fe7b10f569a..790860df2a7 100644
--- a/lisp/emacs-lisp/package.el
+++ b/lisp/emacs-lisp/package.el
@@ -3082,19 +3082,21 @@ package--print-email-button
   "Insert a button whose action will send an email to RECIPIENT.
 NAME should have the form (FULLNAME . EMAIL) where FULLNAME is
 either a full name or nil, and EMAIL is a valid email address."
-  (when (car recipient)
-    (insert (car recipient)))
-  (when (and (car recipient) (cdr recipient))
-    (insert " "))
-  (when (cdr recipient)
-    (insert "<")
-    (insert-text-button (cdr recipient)
-                        'follow-link t
-                        'action (lambda (_)
-                                  (compose-mail
-                                   (format "%s <%s>" (car recipient) (cdr 
recipient)))))
-    (insert ">"))
-  (insert "\n"))
+  (if (stringp recipient)
+      (insert recipient "\n")
+    (when (car recipient)
+      (insert (car recipient)))
+    (when (and (car recipient) (cdr recipient))
+      (insert " "))
+    (when (cdr recipient)
+      (insert "<")
+      (insert-text-button (cdr recipient)
+                          'follow-link t
+                          'action (lambda (_)
+                                    (compose-mail
+                                     (format "%s <%s>" (car recipient) (cdr 
recipient)))))
+      (insert ">"))
+    (insert "\n")))
 
 
 ;;;; Package menu mode.