crypto/x509/by_store.c: Add check for OPENSSL_strdup

crypto/x509/by_store.c: Add check for OPENSSL_strdup

As the potential failure of the OPENSSL_strdup(),
it should be better to check the return value and
return error if fails.

Signed-off-by: Jiasheng Jiang <jiasheng@iscas.ac.cn>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Paul Dale <pauli@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/18593)