Do not allow NPE if CarrierConfigManager service is null. am: 5cf46dc254 am: de4d24b5a7

Original change: https://android-review.googlesource.com/c/platform/packages/services/Telecomm/+/3122851

Change-Id: Id46b66db4e19605114267d24cdb980436feff934
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>