Filter `FieldName <-. [Nothing]` not finding expected results

I'm running into some odd behaviour where the filter FieldName <-. [Just v, Nothing] finds rows where FieldName is either null or v, but FieldName <-. [Nothing] doesn't find any rows at all.

  _johnId <- insert $ Person "John Doe" $ Just 35
  _janeId <- insert $ Person "Jane Doe" Nothing

  selectList [] [] -- finds no one
  selectList [PersonAge <-. [Nothing, Just 35]] [] -- finds John and Jane
  selectList [PersonAge <-. [Just 35]] [] -- finds John
  selectList [PersonAge <-. [Nothing]] [] -- expected to find Jane, but finds no one

Here's a complete repro using sqlite, but I've also observed this in Postgres.

Start by running the complete sqlite reproduction linked in the issue and compare its results with the listed selectList examples. Trace how Persistent builds filters containing Nothing, then check whether the same behavior can be reproduced with Postgres; done means selectList [PersonAge <-. [Nothing]] returns Jane without breaking the Just cases.