Fix onplatform generics crash on macOS

src/Markup/Avalonia.Markup.Xaml.Loader/AvaloniaXamlIlRuntimeCompiler.cs

@@ -198,6 +198,7 @@ namespace Avalonia.Markup.Xaml.XamlIl
             compiler.ParseAndCompile(xaml, uri?.ToString(), null, _sreTypeSystem.CreateTypeBuilder(tb), overrideType);
             var created = tb.CreateTypeInfo();
             clrPropertyBuilder.CreateTypeInfo();
+            indexerClosureType.CreateTypeInfo();
             trampolineBuilder.CreateTypeInfo();
 
             return LoadOrPopulate(created, rootInstance);

src/Markup/Avalonia.Markup.Xaml.Loader/CompilerExtensions/Transformers/AvaloniaXamlIlOptionMarkupExtensionTransformer.cs

@@ -216,7 +216,7 @@ internal class AvaloniaXamlIlOptionMarkupExtensionTransformer : IXamlAstTransfor
             IXamlType contextParameter)
             : base(
             original.Value,
-            new OptionsMarkupExtensionMethod(new OptionsMarkupExtensionNodesContainer(branches, defaultNode), original.Type.GetClrType(), contextParameter),
+            new OptionsMarkupExtensionMethod(new OptionsMarkupExtensionNodesContainer(branches, defaultNode), original.Value.Type.GetClrType(), contextParameter),
             original.Value)
         {
             _contextParameter = contextParameter;