When overriding Model.query() as follows and running upsertGraph() commands on such a model, the onError()callback is called with the internally used ReturnNullException.

class Model extends objection.Model {
  static query(trx) {
    return super.query(trx).onError(err => {
      console.error(err);
    })
  }
}

This is caused by my fix in #2452 for #2233

I have a fix coming up for this issue.