Merge "Null safety check to avoid NPE in rare thread sync issue." into udc-dev am: 21e651ba

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/opt/telephony/+/22163524



Change-Id: I20f71644975d487fb4c5755e68892a1312cbb6b2
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>