[TIMOB-9444] Android: Ti.UI.Tab.open() should not set the window property

var tabGroup = Ti.UI.createTabGroup();

var win1 = Ti.UI.createWindow ({
    title: "Win 1",
    layout: "vertical"
});

var btn1 = Ti.UI.createButton ({
    title: 'Open subwindow',
    top: 20
});

btn1.addEventListener ('click', function (e) {
    var win1a = Ti.UI.createWindow ({
        title: "Win 1a"
    });
    tabGroup.getActiveTab().open (win1a);
});

win1.add (btn1);

var btn2 = Ti.UI.createButton ({
    title: 'get active tab window title',
    top: 20,
});

btn2.addEventListener ('click', function (e) {
    var t = tabGroup.getActiveTab().getWindow ().title;
    alert (t);
});

win1.add (btn2);

var tab1 = Ti.UI.createTab({  
    title:'Win 1',
    window: win1
});

var win2 = Ti.UI.createWindow ({
    title: "Win 2"
});

var tab2 = Ti.UI.createTab({  
    title:'Win 2',
    window: win2
});

tabGroup.addTab(tab1);  
tabGroup.addTab(tab2); 


// open tab group
tabGroup.open();