Fix double free in cookie generation.
GH:
@@ -658,6 +658,7 @@ int tls_construct_ctos_cookie(SSL *s, WPACKET *pkt, unsigned int context,
ret = 1;
end:
OPENSSL_free(s->ext.tls13_cookie);
+ s->ext.tls13_cookie = NULL;
s->ext.tls13_cookie_len = 0;
return ret;
