Only verify skipped buckets if present to reflect skipped bucket changes in aosp/2153240. am: f5f0131161 am: ce729d6fa9

Original change: https://android-review.googlesource.com/c/platform/packages/modules/StatsD/+/2199810

Change-Id: I68457d7db5a82bcdc50ecdcce22673bc3e28b875
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>