fuzz/fuzz_rand.c: Add check for OSSL_LIB_CTX_new
fuzz/fuzz_rand.c: Add check for OSSL_LIB_CTX_new

As the potential failure of the OPENSSL_zalloc(), the OSSL_LIB_CTX_new()
could return NULL.
Therefore, it should be better to check it and return error if fails in
order to guarantee the success of the initialization.

Signed-off-by: Jiasheng Jiang <jiasheng@iscas.ac.cn>

Reviewed-by: Paul Dale <ddec78389666b4f7c9b4d110380c848489a3e4aa@openssl.org>
Reviewed-by: Tomas Mraz <2bc6038c3dfca09b2da23c8b6da8ba884dc2dcc2@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/17738)

openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl