Merge "keymaster: avoid deref'ing nullptr" am: 1e4630d844 am: a05e847177 am: 19361e0a7a

Original change: https://android-review.googlesource.com/c/platform/system/keymaster/+/1555467

Change-Id: I07c45764be8cf02ca8d70fe0375aabf55e35912d