Merge "KeyguardIndication: Allow no message as long as there's an icon" into sc-dev am: a5d01d30 am: 821ca9d4

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/13585185

Change-Id: I0ef15e95938ae1084b16f59b0c83851059e5a969