Fix runtime errors

Emby.Server.Implementations/ApplicationHost.cs

@@ -310,7 +310,9 @@ namespace Emby.Server.Implementations
             {
                 _creatingInstances.Add(type);
                 Logger.LogDebug("Creating instance of {Type}", type);
-                return ActivatorUtilities.CreateInstance(ServiceProvider, type);
+                return ServiceProvider is null
+                    ? Activator.CreateInstance(type)
+                    : ActivatorUtilities.CreateInstance(ServiceProvider, type);
             }
             catch (Exception ex)
             {

src/Jellyfin.Extensions/Json/JsonDefaults.cs

@@ -1,5 +1,6 @@
 using System.Text.Json;
 using System.Text.Json.Serialization;
+using System.Text.Json.Serialization.Metadata;
 using Jellyfin.Extensions.Json.Converters;
 
 namespace Jellyfin.Extensions.Json
@@ -41,7 +42,8 @@ namespace Jellyfin.Extensions.Json
                 new JsonNullableStructConverterFactory(),
                 new JsonDateTimeConverter(),
                 new JsonStringConverter()
-            }
+            },
+            TypeInfoResolver = new DefaultJsonTypeInfoResolver()
         };
 
         private static readonly JsonSerializerOptions _pascalCaseJsonSerializerOptions = new(_jsonSerializerOptions)