bug#64089: 30.0.50; `ldap-search' errors out with `wrong-type-argument listp' when called WITHDN == t

[Jens Schmidt]

Start emacs -Q.  Then:

(require 'ldap)
=> ldap

(setq ldap-host-parameters-alist
      '(("ldap://<host>" .
         (auth simple
          base "dc=<domain>,dc=com"))))
=> (("ldap://<host>" auth simple base "dc=<domain>,dc=com"))

(ldap-search "(uid=<uid>)"
             "ldap://<host>"
             '("mail"))
=> ((("mail" "<name>@<domain>.com")))

(ldap-search "(uid=<uid>)"
             "ldap://<host>"
             '("mail")
             nil
             t)

Error stack:
Debugger entered--Lisp error: (wrong-type-argument listp "dn: 
cn=<NAME>,L=<REGION>,DC=<DOMAIN>,DC=COM")
  ldap-decode-attribute("dn: cn=<NAME>,L=<REGION>,DC=<DOMAIN>,DC=COM")
  mapcar(ldap-decode-attribute ("dn: 
cn=<NAME>,L=<REGION>,DC=<DOMAIN>,DC=COM" ("mail" "<name>@<domain>.com")))

Error cause is pretty obvious: Function `ldap-decode-attribute' expects 
a pair ("dn" "<dn>") and not a string "dn: <dn>" generated by the sexp

  `(setq dn (buffer-substring (point) (line-end-position)))'

in `ldap-search-internal'.

This bug is also present in Emacs 29.

Patch available, will provide in next bug update.