Fix runtime kotlin nullable error in ScreenshotDetectionControllerTest am: b6aaf84246 am: 4e9b309ea3

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/24588598

Change-Id: I31fdbb898d4233fe69b0358b0c23490a6dd809d6
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>