Reproduce steps:
* Use Triple protocol in both consumer and provider,
* The provider works with `-Ddubbo.application.register-mode=instance`
* The consumer works with `-Ddubbo.application.service-discovery.migration=FORCE_APPLICATION`

Above test case will throw following errors:
```shell
[29/09/21 11:52:35:035 CST] NettyClientWorker-3-3  WARN channel.ChannelInitializer: Failed to initialize a channel. Closing: [id: 0xc1ba4a78]
java.lang.NullPointerException
	at org.apache.dubbo.registry.client.InstanceAddressURL.getScopeModel(InstanceAddressURL.java:498)
	at org.apache.dubbo.rpc.protocol.tri.TripleHttp2Protocol.configClientPipeline(TripleHttp2Protocol.java:76)
	at org.apache.dubbo.remoting.api.Connection$1.initChannel(Connection.java:115)
	at org.apache.dubbo.remoting.api.Connection$1.initChannel(Connection.java:102)
	at io.netty.channel.ChannelInitializer.initChannel(ChannelInitializer.java:129)
	at io.netty.channel.ChannelInitializer.handlerAdded(ChannelInitializer.java:112)
	at io.netty.channel.AbstractChannelHandlerContext.callHandlerAdded(AbstractChannelHandlerContext.java:938)
	at io.netty.channel.DefaultChannelPipeline.callHandlerAdded0(DefaultChannelPipeline.java:609)
	at io.netty.channel.DefaultChannelPipeline.access$100(DefaultChannelPipeline.java:46)
	at io.netty.channel.DefaultChannelPipeline$PendingHandlerAddedTask.execute(DefaultChannelPipeline.java:1463)
	at io.netty.channel.DefaultChannelPipeline.callHandlerAddedForAllHandlers(DefaultChannelPipeline.java:1115)
	at io.netty.channel.DefaultChannelPipeline.invokeHandlerAddedIfNeeded(DefaultChannelPipeline.java:650)
	at io.netty.channel.AbstractChannel$AbstractUnsafe.register0(AbstractChannel.java:502)
	at io.netty.channel.AbstractChannel$AbstractUnsafe.access$200(AbstractChannel.java:417)
	at io.netty.channel.AbstractChannel$AbstractUnsafe$1.run(AbstractChannel.java:474)
	at io.netty.util.concurrent.AbstractEventExecutor.safeExecute(AbstractEventExecutor.java:164)
	at io.netty.util.concurrent.SingleThreadEventExecutor.runAllTasks(SingleThreadEventExecutor.java:472)
	at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:500)
	at io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:989)
	at io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74)
	at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30)
	at java.lang.Thread.run(Thread.java:748)
```
ReferenceConfig<HelloService> reference = new ReferenceConfig<HelloService>();
            reference.setRegistry(new RegistryConfig(RegistryConfig.NO_AVAILABLE));
            reference.setInterface(HelloService.class);
            reference.setUrl("dubbo://127.0.0.1:12345");
            consumerBootstrap = DubboBootstrap.newInstance()
                    .application(new ApplicationConfig("consumer"))
                    .reference(reference)
                    .start();
            HelloService helloService = consumerBootstrap.getCache().get(reference);
            String hello = helloService.sayHello("hello");
            assertEquals("Hello, hello", hello);
        } finally {
            providerContext.close();
            if (consumerBootstrap != null) {
                consumerBootstrap.stop();
            }
        }
    }
    @Test
    @SuppressWarnings("unchecked")
    public void testProviderNestedService() {
        ClassPathXmlApplicationContext ctx = new ClassPathXmlApplicationContext(resourcePath + "/provider-nested-service.xml");
        try {
            ctx.start();
            ServiceConfig<DemoService> serviceConfig = (ServiceConfig<DemoService>) ctx.getBean("serviceConfig");
            assertNotNull(serviceConfig.getProvider());
            assertEquals(2000, serviceConfig.getProvider().getTimeout().intValue());
            ServiceConfig<DemoService> serviceConfig2 = (ServiceConfig<DemoService>) ctx.getBean("serviceConfig2");
            assertNotNull(serviceConfig2.getProvider());
            assertEquals(1000, serviceConfig2.getProvider().getTimeout().intValue());