Fix potential double-free

Fix potential double-free

The `sk` variable is assigned to `s->session->peer_chain`.
If `ssl3_digest_cached_records()` were to fail, then `sk` would still be
non-NULL, and subsequently freed on the error return. When the session
is freed, it will then attempt to free `s->session->peer_chain`,
resulting in a double-free (of `sk`).

Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/16309)