Consider null as a valid geo object

milli/src/update/index_documents/enrich.rs

@@ -395,6 +395,7 @@ pub fn validate_geo_from_json(id: &DocumentId, bytes: &[u8]) -> Result<StdResult
             (Some(_), None) => Ok(Err(MissingLongitude { document_id: debug_id() })),
             (None, None) => Ok(Err(MissingLatitudeAndLongitude { document_id: debug_id() })),
         },
+        Value::Null => Ok(Ok(())),
         value => Ok(Err(NotAnObject { document_id: debug_id(), value })),
     }
 }

milli/src/update/index_documents/extract/extract_geo_points.rs

@@ -59,6 +59,7 @@ pub fn extract_geo_points<R: io::Read + io::Seek>(
         } else if lat.is_some() && lng.is_none() {
             return Err(GeoError::MissingLongitude { document_id: document_id() })?;
         }
+        // else => the _geo object was `null`, there is nothing to do
     }
 
     writer_into_reader(writer)