ionic2: ion-tabs tabs.getSelected().index got a Error: Cannot read property 'index' of null

[jeneser]

Ionic version: (check one with "x")
[ ] 1.x
[ x ] 2.x

I'm submitting a ... (check one with "x")
[ x ] bug report
[ ] feature request
[ ] support request => Please do not submit support requests here, use one of these channels: https://forum.ionicframework.com/ or http://ionicworldwide.herokuapp.com/

Current behavior:

Runtime Error
Error in ./HomePage class HomePage - caused by: Cannot read property 'index' of null

Stack
TypeError: Cannot read property 'index' of null
    at HomePage.onTabsChange (http://localhost:8100/build/main.js:56074:44)
    at CompiledTemplate.proxyViewClass.View_HomePage0.handleEvent_27 (/AppModule/HomePage/component.ngfactory.js:599:34)
    at CompiledTemplate.proxyViewClass.<anonymous> (http://localhost:8100/build/main.js:96697:37)
    at SafeSubscriber.schedulerFn [as _next] (http://localhost:8100/build/main.js:35084:36)
    at SafeSubscriber.__tryOrUnsub (http://localhost:8100/build/main.js:87920:16)
    at SafeSubscriber.next (http://localhost:8100/build/main.js:87869:22)
    at Subscriber._next (http://localhost:8100/build/main.js:87822:26)
    at Subscriber.next (http://localhost:8100/build/main.js:87786:18)
    at EventEmitter.Subject.next (http://localhost:8100/build/main.js:19527:25)
    at EventEmitter.emit (http://localhost:8100/build/main.js:35064:76)

Expected behavior:

When i used var tab_index = this.tabs.getSelected().index; in ionViewDidEnter() and onSlideDidChange(), all going well.I can get index.

But , i write var tab_index = this.tabs.getSelected().index; into onTabsChange(){}.I got the Runtime Error Cannot read property 'index' of null

Steps to reproduce:

reproduce:
http://plnkr.co/edit/BAy0Z7?p=preview

Related code:
Other information:

Ionic info: (run ionic info from a terminal/cmd prompt and paste output below):

Ionic Framework: 2.0.1
Ionic Native: 2.4.1
Ionic App Scripts: 1.1.0
Angular Core: 2.2.1
Angular Compiler CLI: 2.2.1
Node: 6.9.2
OS Platform: Linux 4.4
Navigator Platform: Linux x86_64
User Agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Ubuntu Chromium/55.0.2883.87 Chrome/55.0.2883.87 Safari/537.36

Similar:
#10523

[ionitron-bot]

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