Testing against 2.4.11

This works:

MyModel.where(foo_id: nil)

But this doesn't work (it only captures documents where foo_id was not nil):

MyModel.any_in(foo_id: [nil,Foo.first.id])

This also doesn't work (it captures no documents):

MyModel.any_in(foo_id: [nil])

But equivalent queries run directly against MongoDB do work:

db.my_models.find({foo_id: { $in : [null] }})
db.my_models.find({foo_id: { $in : [null,ObjectId("4fcfa5d0202cb17b63000003")] }})

The criteria_spec also doesn't handle the case where nil is passed to any_in