This is a regression test for a fix included in
https://github.com/rails/rails/commit/bad9bfbea6d6af9dc28583e08a49492668087393.

Without that change, this test would fail with:

    ActiveRecord::StatementInvalid: SQLite3::SQLException: near "WHERE": syntax error: UPDATE "topics" SET "replies_count" = COALESCE("replies_count", 0) - 1,  WHERE "topics"."id" = ?