Prevent possible null ref warnings.

src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/DynamicResourceExtension.cs

@@ -59,7 +59,7 @@ namespace Avalonia.Markup.Xaml.MarkupExtensions
 
         private T GetAnchor<T>(ITypeDescriptorContext context) where T : class
         {
-            var schemaContext = context.GetService<IXamlSchemaContextProvider>()?.SchemaContext;
+            var schemaContext = context.GetService<IXamlSchemaContextProvider>().SchemaContext;
             var ambientProvider = context.GetService<IAmbientProvider>();
             var xamlType = schemaContext.GetXamlType(typeof(T));
 

src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/StaticResourceExtension.cs

@@ -29,7 +29,7 @@ namespace Avalonia.Markup.Xaml.MarkupExtensions
         public override object ProvideValue(IServiceProvider serviceProvider)
         {
             var context = (ITypeDescriptorContext)serviceProvider;
-            var schemaContext = context.GetService<IXamlSchemaContextProvider>()?.SchemaContext;
+            var schemaContext = context.GetService<IXamlSchemaContextProvider>().SchemaContext;
             var ambientProvider = context.GetService<IAmbientProvider>();
             var resourceProviderType = schemaContext.GetXamlType(typeof(IResourceNode));
             var ambientValues = ambientProvider.GetAllAmbientValues(resourceProviderType);