gpg: Fix attempt to double free an UID structure.

gpg: Fix attempt to double free an UID structure.

* g10/getkey.c (get_best_pubkey_byname): Set released .UID to NULL.
--

Phil Pennock reported an assertion failure when doing

  % gpg --auto-key-locate dane --locate-keys someone
  gpg: Ohhhh jeeee: Assertion "uid->ref > 0" in \
         free_user_id failed (free-packet.c:310)

on his keyring.  This patch is not tested but a good guess.

Signed-off-by: Werner Koch <wk@gnupg.org>
(cherry picked from commit 4a130bbc2c2f4be6e8c6357512a943f435ade28f)

Gbp-Pq: Name 0048-gpg-Fix-attempt-to-double-free-an-UID-structure.patch