Fix server-side filtering on nested array filter

This fixes a bug that made it impossible to use a custom filter on an array field that was projected on the server side. For example, if you have an item like {a: [{b: 'c'}]}, you can project fields inside the array when publishing on the server by using fields: {"a.b": 1}. However, if you wanted to filter on a particular item in the array, you couldn't use a field a.0.b since it didn't match the server-side projection. This change allows filtering on any array index if the array field is projected.