[TIMOB-24367] Android: Going back to the tabgroup with android back button crashes app with "java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.Object ti.modules.titanium.ui.TabGroupProxy.getProperty(java.lang.String)"

var win1 = Ti.UI.createWindow({
    backgroundColor: 'blue',
    title: 'Blue'
});

var lbl = Ti.UI.createLabel({text: 'I am a blue window.'});

lbl.addEventListener('click', function(){
	Ti.UI.createWindow().open();	
});

win1.add(lbl);

var win2 = Ti.UI.createWindow({
    backgroundColor: 'red',
    title: 'Red'
});

win2.add(Ti.UI.createLabel({text: 'I am a red window.'}));

var tab1 = Ti.UI.createTab({
    window: win1,
    title: 'Blue'
}),
tab2 = Ti.UI.createTab({
    window: win2,
    title: 'Red'
}),
tabGroup = Ti.UI.createTabGroup({
    tabs: [tab1, tab2]
});
tabGroup.open();

[ERROR] :  TiApplication: (main) [8300,8300] Sending event: exception on thread: main msg:java.lang.RuntimeException: Unable to start activity ComponentInfo{com.app.timob24253/org.appcelerator.titanium.TiActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.Object ti.modules.titanium.ui.TabGroupProxy.getProperty(java.lang.String)' on a null object reference; Titanium 6.1.0,2017/01/31 13:23,undefined
[ERROR] :  TiApplication: java.lang.RuntimeException: Unable to start activity ComponentInfo{com.app.timob24253/org.appcelerator.titanium.TiActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.Object ti.modules.titanium.ui.TabGroupProxy.getProperty(java.lang.String)' on a null object reference
[ERROR] :  TiApplication: 	at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2416)
[ERROR] :  TiApplication: 	at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
[ERROR] :  TiApplication: 	at android.app.ActivityThread.-wrap11(ActivityThread.java)
[ERROR] :  TiApplication: 	at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
[ERROR] :  TiApplication: 	at android.os.Handler.dispatchMessage(Handler.java:102)
[ERROR] :  TiApplication: 	at android.os.Looper.loop(Looper.java:148)
[ERROR] :  TiApplication: 	at android.app.ActivityThread.main(ActivityThread.java:5417)
[ERROR] :  TiApplication: 	at java.lang.reflect.Method.invoke(Native Method)
[ERROR] :  TiApplication: 	at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
[ERROR] :  TiApplication: 	at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
[ERROR] :  TiApplication: Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.Object ti.modules.titanium.ui.TabGroupProxy.getProperty(java.lang.String)' on a null object reference
[ERROR] :  TiApplication: 	at ti.modules.titanium.ui.widget.tabgroup.TiUIActionBarTabGroup.addTab(TiUIActionBarTabGroup.java:338)
[ERROR] :  TiApplication: 	at ti.modules.titanium.ui.TabGroupProxy.handlePostOpen(TabGroupProxy.java:396)
[ERROR] :  TiApplication: 	at ti.modules.titanium.ui.TabGroupProxy.windowCreated(TabGroupProxy.java:371)
[ERROR] :  TiApplication: 	at org.appcelerator.titanium.TiActivityWindows.windowCreated(TiActivityWindows.java:33)
[ERROR] :  TiApplication: 	at org.appcelerator.titanium.TiBaseActivity.windowCreated(TiBaseActivity.java:559)
[ERROR] :  TiApplication: 	at org.appcelerator.titanium.TiBaseActivity.onCreate(TiBaseActivity.java:673)
[ERROR] :  TiApplication: 	at org.appcelerator.titanium.TiActivity.onCreate(TiActivity.java:21)
[ERROR] :  TiApplication: 	at android.app.Activity.performCreate(Activity.java:6251)
[ERROR] :  TiApplication: 	at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1107)
[ERROR] :  TiApplication: 	at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2369)
[ERROR] :  TiApplication: 	... 9 more