Merge "[Telephony] Return if context is null when register TelephonyCallback" am: a805d39229 am: 51f11f9b0b am: aab9659d41

Original change: https://android-review.googlesource.com/c/platform/frameworks/base/+/1644386

Change-Id: Iee971b6fdac174392e75e1ae49ef09446faf1257