Fix null pointer from PowerUsageFeatureProvider

Some locations did not check if the returned value was null before
doing operations on them and could crash. This CL changes those
spots to take that into account.

Test: b/72463854 will add in follow up to unblock dogfood
Bug: 72350595
Change-Id: I0ace5c0ab4a8aa9fd5b09d41d6f986143246f059