demos/bio/sconnect.c: Add check for BIO_new()

demos/bio/sconnect.c: Add check for BIO_new()

Add check for the return value of BIO_new() to guarantee the success.

Fixes: 0f113f3ee4 ("Run util/openssl-format-source -v -c .")
Signed-off-by: Jiasheng Jiang <jiashengjiangcool@gmail.com>
Reviewed-by: Dmitry Belyavskiy <beldmit@gmail.com>
Reviewed-by: Frederik Wedel-Heinen <fwh.openssl@gmail.com>
Reviewed-by: Neil Horman <nhorman@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/27919)