### Environment

* Dubbo version: 3.0

### Steps to reproduce this issue
测试dubbo-samples项目的AnnotationServicesIT.testGreeting方法时，偶尔会出现服务端超时触发此异常。
手工触发方法：
修改AnnotationAction.java的greetingService服务引用对象的method超时注解，从3000改为1000（服务端代码里有2000毫秒sleep），然后运行就会遇到NPE：
```
java.lang.NullPointerException 
	at org.apache.dubbo.rpc.protocol.dubbo.DecodeableRpcResult.decode(DecodeableRpcResult.java:85)
```
DecodeableRpcResult 85行代码：```if (invocation.getServiceModel() != null) { ```
服务端超时，此处invocation为null。
break;
            case DubboCodec.RESPONSE_WITH_EXCEPTION:
                handleException(in);
                break;
            case DubboCodec.RESPONSE_NULL_VALUE_WITH_ATTACHMENTS:
                handleAttachment(in);
                break;
            case DubboCodec.RESPONSE_VALUE_WITH_ATTACHMENTS:
                handleValue(in);
                handleAttachment(in);
                break;
            case DubboCodec.RESPONSE_WITH_EXCEPTION_WITH_ATTACHMENTS:
                handleException(in);
                handleAttachment(in);
                break;
            default:
                throw new IOException("Unknown result flag, expect '0' '1' '2' '3' '4' '5', but received: " + flag);
        }
        if (in instanceof Cleanable) {
            ((Cleanable) in).cleanup();
        }
        return this;
    }
    @Override
    public void decode() throws Exception {
        if (!hasDecoded && channel != null && inputStream != null) {
            try {
                if (invocation != null) {
                    if (ConfigurationUtils.getSystemConfiguration(channel.getUrl().getScopeModel()).getBoolean(SERIALIZATION_SECURITY_CHECK_KEY, true)) {
                        Object serializationTypeObj = invocation.get(SERIALIZATION_ID_KEY);