AlgoliaIndexReference.facetQuery should accept facets without objectID

[Chralu]

Flutter version: 2.10.3 (stable)

Describe the bug
When querying a simple string facet, library throws a "type 'Null' is not a subtype of type 'String'" error.

To Reproduce
Steps to reproduce the behavior:

1. In Algolia settings, setup a facet on a string property
2. In your Flutter code, run a query like :

final algolia = Algolia.init(
      applicationId: <my_application_id>,
      apiKey: <my_api_key>,
);

await algolia
        ?.index(<my_index>)
        .facetQuery(<my_simple_facet_name>);

It will throw an error when converting Algolia response to AlgoliaFacetValueSnapshot.

Expected behavior
AlgoliaFacetValueSnapshot.objectID should accept null value.

[nhathiwala]

This has been fix in 1.0.5