Fix Settings crash when setting a null ringtone am: ec3ae8bb am: 39759724 am: 928a73c8

Original change: https://googleplex-android-review.googlesource.com/c/platform/packages/apps/Settings/+/18400413



Change-Id: If39c9c61e974eb69a59d9c13dd758efec33da859
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>