Trouble with equality predicate

const emptyFields = await ctx.db
  .query("bookmarks")
  .withSearchIndex("by_userId", q =>
     q.search("userId", userId).eq("embedding", undefined || [] || null), // the fields with [] are selected correctly. but the fields that are "unset" are not selected. how can i select them?
  )
  .collect();

const emptyFields = await ctx.db
  .query("bookmarks")
  .withSearchIndex("by_userId", q =>
     q.search("userId", userId).eq("embedding", undefined || [] || null), // the fields with [] are selected correctly. but the fields that are "unset" are not selected. how can i select them?
  )
  .collect();