CryptoPkg/BaseCryptLib: fix NULL dereference

AuthenticodeVerify() calls OpenSSLs d2i_PKCS7() API to parse asn encoded
signed authenticode pkcs#7 data. when this successfully returns, a type
check is done by calling PKCS7_type_is_signed() and then
Pkcs7->d.sign->contents->type is used. It is possible to construct an asn1
blob that successfully decodes and have d2i_PKCS7() return a valid pointer
and have PKCS7_type_is_signed() also return success  but have Pkcs7->d.sign
be a NULL pointer.

Looking at how PKCS7_verify() [inside of OpenSSL] implements checking for
pkcs7 structs it does the following:
- call PKCS7_type_is_signed()
- call PKCS7_get_detached()
Looking into how PKCS7_get_detatched() is implemented, it checks to see if
p7->d.sign is NULL or if p7->d.sign->contents->d.ptr is NULL.

As such, the fix is to do the same as OpenSSL after calling d2i_PKCS7().
- Add call to PKS7_get_detached() to existing error handling

Cc: Chao Zhang <chao.b.zhang@intel.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Signed-off-by: Jian J Wang <jian.j.wang@intel.com>
Cherry-picked-from: https://github.com/tianocore/edk2/commit/26442d11e620a9e81c019a24a4ff38441c64ba10

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