System.NullReferenceException: Object reference not set to an instance of an object.
at MongoDB.Driver.FieldValueSerializerHelper.ConvertIfPossibleSerializer2.TryConvertValue(TFrom value, TTo& convertedValue)
at MongoDB.Driver.FieldValueSerializerHelper.ConvertIfPossibleSerializer2.Serialize(BsonSerializationContext context, BsonSerializationArgs args, TFrom value
at MongoDB.Bson.Serialization.IBsonSerializerExtensions.Serialize[TValue](IBsonSerializer1 serializer, BsonSerializationContext context, TValue value)
at MongoDB.Driver.OperatorUpdateDefinition2.Render(IBsonSerializer1 documentSerializer, IBsonSerializerRegistry serializerRegistry)
at MongoDB.Driver.CombinedUpdateDefinition1.Render(IBsonSerializer1 documentSerializer, IBsonSerializerRegistry serializerRegistry)
at MongoDB.Driver.MongoCollectionImpl1.ConvertWriteModelToWriteRequest(WriteModel1 model, Int32 index)
at System.Linq.Enumerable.<SelectIterator>d__52.MoveNext()
at System.Collections.Generic.List1..ctor(IEnumerable1 collection)
at System.Linq.Enumerable.ToList[TSource](IEnumerable1 source)
at MongoDB.Driver.Core.Operations.BulkMixedWriteOperation..ctor(CollectionNamespace collectionNamespace, IEnumerable1 requests, MessageEncoderSettings messageEncoderSettings)
at MongoDB.Driver.MongoCollectionImpl1.CreateBulkWriteOperation(IEnumerable1 requests, BulkWriteOptions options)
at MongoDB.Driver.MongoCollectionImpl1.<BulkWriteAsync>d__26.MoveNext()
-- End of stack trace from previous location where exception was thrown ---
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at MongoDB.Driver.MongoCollectionImpl1.d__911.MoveNext()
-- End of stack trace from previous location where exception was thrown ---
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd(Task task)
at MongoDB.Driver.MongoCollectionBase1.d__93.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)