System.Reflection.TargetInvocationException: Адресат вызова создал исключение. ---> System.ArgumentNullException: Значение не может быть неопределенным.
Имя параметра: xamlType
   в Portable.Xaml.XamlWriterInternalBase.WriteStartObject(XamlType xamlType)
   в Portable.Xaml.XamlObjectWriter.WriteStartObject(XamlType xamlType)
   в Portable.Xaml.XamlWriter.WriteNode(XamlReader reader)
   в Portable.Xaml.XamlServices.Transform(XamlReader xamlReader, XamlWriter xamlWriter, Boolean closeWriter)
   в Avalonia.Markup.Xaml.AvaloniaXamlLoaderPortableXaml.LoadFromReader(XamlReader reader, AvaloniaXamlContext context)
   в Avalonia.Markup.Xaml.AvaloniaXamlLoaderPortableXaml.Load(Stream stream, Object rootInstance, Uri uri)
   в Avalonia.Markup.Xaml.AvaloniaXamlLoaderPortableXaml.Load(Uri uri, Uri baseUri, Object rootInstance)
   в Avalonia.Markup.Xaml.Styling.StyleInclude.get_Loaded()
   в Avalonia.Markup.Xaml.Styling.StyleInclude.Avalonia.Styling.ISetStyleParent.NotifyResourcesChanged(ResourcesChangedEventArgs e)
   в Avalonia.Styling.Styles.<.ctor>b__2_0(IStyle x)
   в Avalonia.Collections.AvaloniaListExtensions.<>c__DisplayClass0_0`1.<ForEachItem>b__0(Int32 _, T i)
   в Avalonia.Collections.AvaloniaListExtensions.<>c__DisplayClass1_0`1.<ForEachItem>g__Add0(Int32 index, IList items)
   в Avalonia.Collections.AvaloniaListExtensions.<>c__DisplayClass1_0`1.<ForEachItem>b__2(Object _, NotifyCollectionChangedEventArgs e)
   в Avalonia.Collections.AvaloniaList`1.NotifyAdd(IList t, Int32 index)
   в Avalonia.Collections.AvaloniaList`1.Add(T item)
   в lambda_method(Closure , Object , Object )
   в Portable.Xaml.MemberExpressionExtensions.<>c__DisplayClass8_0.<BuildCallExpression>b__0(Object instance, Object value)
   в Portable.Xaml.Schema.XamlTypeInvoker.AddToCollection(Object instance, Object item)
   в Portable.Xaml.XamlObjectWriterInternal.AddToCollectionIfAppropriate(XamlType xt, XamlMember xm, Object parent, Object obj, Object keyObj)
   в Portable.Xaml.XamlObjectWriterInternal.StoreAppropriatelyTypedValue(ObjectState state, MemberAndValue ms, Object obj, Object keyObj)
   в Portable.Xaml.XamlObjectWriterInternal.OnWriteEndObject()
   в Portable.Xaml.XamlWriterInternalBase.WriteEndObject()
   в Portable.Xaml.XamlObjectWriter.WriteEndObject()
   в Portable.Xaml.XamlWriter.WriteNode(XamlReader reader)
   в Portable.Xaml.XamlServices.Transform(XamlReader xamlReader, XamlWriter xamlWriter, Boolean closeWriter)
   в Avalonia.Markup.Xaml.AvaloniaXamlLoaderPortableXaml.LoadFromReader(XamlReader reader, AvaloniaXamlContext context)
   в Avalonia.Markup.Xaml.AvaloniaXamlLoaderPortableXaml.Load(Stream stream, Object rootInstance, Uri uri)
   в Avalonia.Markup.Xaml.AvaloniaXamlLoaderPortableXaml.Load(Type type, Object rootInstance)
   в Avalonia.Markup.Xaml.AvaloniaXamlLoaderPortableXaml.Load(Object obj)