NSObjectExtentions NullReferenceException crash

[barrysohl]

We have a FirestoreObject that causes a NullReferenceException deep in Firestore code during serialization for SetDataAsync. Statckrace is below.

The crash occurs in the following spot at Plugin.Firebase.Firestore.Platforms.iOS.Extensions.NSObjectExtensions.ToNSObject where @this is null.

public static NSObject ToNSObject(this object @this)
    {
      switch (@this)

and then crashes further on in the method when it hits this line:
interpolatedStringHandler.AppendFormatted<Type>(@this.GetType());

The same thing happens whether the call is batched or not, in case that matters. Any ideas? Thanks in advance!

System.NullReferenceException: Object reference not set to an instance of an object.
   at Plugin.Firebase.Firestore.Platforms.iOS.Extensions.NSObjectExtensions.ToNSObject(Object this)
   at Plugin.Firebase.Firestore.Platforms.iOS.Extensions.ListExtensions.ToNSArray(IList this)
   at Plugin.Firebase.Firestore.Platforms.iOS.Extensions.NSObjectExtensions.ToNSObject(Object this)
   at Plugin.Firebase.Firestore.Platforms.iOS.Extensions.DictionaryExtensions.ToDictionary(Object this)
   at Plugin.Firebase.Firestore.Platforms.iOS.Extensions.NSObjectExtensions.ToNSObject(IFirestoreObject this)
   at Plugin.Firebase.Firestore.Platforms.iOS.Extensions.NSObjectExtensions.ToNSObject(Object this)
   at Plugin.Firebase.Firestore.Platforms.iOS.Extensions.DictionaryExtensions.ToDictionary(Object this)
   at Plugin.Firebase.Firestore.Platforms.iOS.WriteBatchWrapper.SetData(IDocumentReference document, Object data, SetOptions options)
--- user code

[barrysohl]

A little bit more info on this one... This happens if there is an IList property within an IFirestoreObject that is in turn a property witihn an IFirestoreObject (see code below). We have had trouble in multiple places with our hierarchical data model that were not a problem previously with Plugin.Firestore.

public class ClassA : IFirestoreObject
{
      [FirestoreProperty("classb")] public ClassB { get; set; }
}

public class ClassB : IFirestoreObject
{
      [FirestoreProperty("strings")] public IList<string> Strings { get; set; }
}