The Sept migration MakePlayListPictureColumnsOptional altered the
PlayLists picture columns to nullable:true when they were already
nullable:true (set back in MakePlayListPicturesNullable, two months
earlier) — a dead migration left over from making the Pictures
navigation itself optional, which produces no actual schema change.
Verified with `dotnet ef migrations has-pending-model-changes` and a
full migration run against a fresh Postgres container that removing
it introduces no drift.
Also add a test for updating a playlist that has no picture yet,
which was the one Pictures-related state transition without coverage.
Admin
a4ca1f32d3