Fix wild pointer dereference in make_ocsp_response()

Fix wild pointer dereference in make_ocsp_response()

The function OCSP_basic_add1_status() will return NULL on malloc failure.
However the return value is not checked before being passed to
OCSP_SINGLERESP_add1_ext_i2d(), and there is a wild field pointer,
which could lead to wild pointer dereference.

Fix this by adding return value check

Reviewed-by: Kurt Roeckx <kurt@roeckx.be>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/18081)