CryptoPkg: Fix the dereferenced pointer issue

This patch is to fix one dereferenced pointer issue in new
Pkcs7GetAttachedContent API, and add the memory allocation
failure check.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Qin Long <qin.long@intel.com>
Reviewed-by: Ye Ting <ting.ye@intel.com>

git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@17731 6f19259b-4bc3-4df7-8a09-765794883524
1 file changed