[automerger skipped] Fix kotlin nullable errors in ThemePicker am: 48b4225329 am: 4264f983ed -s ours am: f5c57e3a4f -s ours

am skip reason: Merged-In If13ac9b81cfe65730d5ce270e9409bc97cef75ec with SHA-1 2d4a9f40c3 is already in history

Original change: https://android-review.googlesource.com/c/platform/packages/apps/ThemePicker/+/2702153

Change-Id: Ia8fb697a4ce5ca467920576bfd37a87a958d0619
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>