Merge "Fix NPE in BootReceiver.addTombstoneToDropBox." into sc-qpr1-dev am: 94d3762fba

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/15857254

Change-Id: I7202abbc1e7f796c7a0c1ab13b2058ca3248125a