Collection Discounts in lineItem is not initialised

[Anatfe]

The ShoppingCart can return with null LineItem Discount. But Virto.XCart is expecting <NonNullGraphType

Error:
GraphQL.Execution.UnhandledError: Error trying to resolve field 'discounts'.\n ---> System.InvalidOperationException: Cannot return null for a non-null type. Field: discounts, Type: [DiscountType!]