Merge "SystemCertificateSource: Mitigate NPE when checking updateable certs directory" into main am: b7e715d8d9 am: 70c4c4f886

Original change: https://android-review.googlesource.com/c/platform/frameworks/base/+/3165417

Change-Id: Ibe25e36d666597428caa28ec7666dbdacce1e171
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>