Custom Types Serializer are broken

Version: 3.1.1-RC1
Delphi: 10.2 Tokyo

In the readme is the new registration for custom serializers descriped as
Changed! Custom Types Serializer must be registered by media-type only, without charset definition (e.g. just application/json and not application/json;charset=utf-8)

I want to add some custom type handlers, but it seems to be broken.
How to reproduce:

Open up the renders_spring4d_nullable sample
compile and run
open the URL localhost:8080/api/parent/1
Exception EMVCSerializationException will be raised

Since the registration is:

delphimvcframework/samples/renders_spring4d_nullables/WebModuleU.pas

Lines 67 to 68 in 10f36ca

    
           FMVC.Serializers.Items['application/json'] 
        
             .RegisterTypeSerializer(typeinfo(Nullable<System.Integer>), TNullableIntegerSerializer.Create);

... the serializer do not found them.
When I backport the registration to BuildContentType('application/json', 'utf-8') it works again.

FIXED IN 3.1.1-beryllium-RC3

	FMVC.Serializers.Items['application/json']
	.RegisterTypeSerializer(typeinfo(Nullable<System.Integer>), TNullableIntegerSerializer.Create);