Change null-handling strategy for Java example

This satisfies the GeoJSON JSON Schema's requirement that the geometry
key be present, even when there is no value.

I'm not sure how best to handle filtering null extension keys.

A follow-on patch will regenerate the dotnet output.

Signed-off-by: Alex Nelson <[email protected]>

java/case2geo/src/main/java/org/caseontology/examples/GeoReader.java

@@ -87,7 +87,7 @@ public String run() {
             List<GeoRecord> records = resultToObjects(result);
 
             // Convert the list of GeoRecord objects to a GeoJSON string and return the string
-            Gson gson = new GsonBuilder().setPrettyPrinting().create();
+            Gson gson = new GsonBuilder().serializeNulls().setPrettyPrinting().create();
             Root geoJSON = recordsToGeoJSON(records);
             return gson.toJson(geoJSON);
         } catch (IOException e) {