When trying to index a collection with a 2dsphere index, even with the sparse option in the nightly build (7/3), the index creation throws an error if some documents have a null value for the coordinates field (not a missing key).

Specifically, this is a collection of tweets directly from the twitter API - the "coordinates" field has a geojson structure if there is geocoding data, but if there is none, the "coordinates" field still exists and has a null value.

The error is:

"Can't parse geometry from element: coordinates: null"