[Robustness] protect get battery stats from DeadSystemException

Refine the original workaround patch in the ag/15527095 from NPE to
return default BatteryUsageStats instance as we merged in the
ag/15919139 (align the same solution).

Bug: 195306545
Test: make SettingsRoboTests
Change-Id: Ic03e8296d16ecb8629155f75727e9cde48c303eb
5 files changed