Exit the App when the default scenario is returned

[Xiao-HuangShu]

Version

Tell us which versions you are using: 4.0.0-beta.24

• react-native-router-flux 4.0.0-beta.24
• react-native 0.51.0
  ###I have four scenarios, A, B, C, D, A is the default scene, when I click to D scene in turn, I click the back button and in theory should be returned to A scene, but it directly out of the App, here is my code

[Xiao-HuangShu]

This is manipulating GIF：

This is the code：
`import { Router, Scene, Actions, Tabs, Stack } from 'react-native-router-flux'
import { createStore, applyMiddleware, compose, combineReducers } from 'redux'
import { connect, Provider } from 'react-redux'
import thunkMiddleware from 'redux-thunk'

// 全局异常处理
import ErrorUtils from 'ErrorUtils'
ErrorUtils.setGlobalHandler(e => {
console.log('错误处理',e);
})

import React, { Component,PropTypes } from 'react';
import {
StyleSheet,
Text,
View
} from 'react-native';
import TabIcon from './app/components/tabIcon'
import Index from './app/components/index'
import My from './app/components/my'

import * as reducers from './app/reducers'
// http://www.redux.org.cn/docs/api/combineReducers.html
const reducer = combineReducers({
...reducers,
})
const RouterWithRedux = connect()(Router)
const middleware = [thunkMiddleware]
// compose(...functions)从右到左来组合多个函数 ,当需要把多个 store 增强器 依次执行的时候，需要用到它,http://www.redux.org.cn/docs/api/compose.html
const store = compose(
// http://www.redux.org.cn/docs/api/applyMiddleware.html
applyMiddleware(...middleware)
)(createStore)(reducer)

export default class App extends Component<{}> {

render() {
    return (
        <Provider store={store}>
            <RouterWithRedux scenes={scenes} >
            </RouterWithRedux>
        </Provider>
    );
}

}

const scenes = Actions.create(

<Stack hideNavBar key="stack" titleStyle={{ alignSelf: 'center' }} >


















)

const styles = StyleSheet.create({
container: {
flex: 1,
justifyContent: 'center',
alignItems: 'center',
backgroundColor: '#F5FCFF',
}
});

// 如果不是开发环境，提示为空
if (!DEV) {
global.console = {
info: () => {},
log: () => {},
warn: () => {},
debug: () => {},
error: () => {},
};
}
`
I don't know why some code is missing, I added a picture to fill the code

[Blapi]

Check #2737