Initialize array pointer to nullptr am: 80019eb5c1 am: 8145973fe7 am: 50b71aaf5d am: 39c17dc7cd

Original change: https://android-review.googlesource.com/c/platform/system/keymaster/+/1778106

Change-Id: I9f45381f494357dbe241c5b2cd71268418f319c8