BIO_new_from_core_bio: Check for NULL pointer after calling get_globals

BIO_new_from_core_bio: Check for NULL pointer after calling get_globals

The get_globals could return NULL, for example,
CRYPTO_THREAD_read_lock() failed.
Therefore, just checking the member of 'bcgbl' is not enough.
We need to check 'bcgbl' itself too in order to avoid the dereference of
the NULL pointer.
And the caller of ossl_bio_init_core(), OSSL_LIB_CTX_new_from_dispatch()
in `crypto/context.c`, has already checked return value and dealed with
the situation if it returns 0.

Signed-off-by: Jiasheng Jiang <jiasheng@iscas.ac.cn>
Reviewed-by: Paul Dale <pauli@openssl.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/17581)