[TIMOB-3231] iOS: Keyboard Toolbar is not displayed at modal window.

Ti.UI.TextArea.keyboardToolbar is not displayed at modal window. (Titanium Mobile 1.6 / iOS SDK 4.2)
It is no problem in Titanium Mobile 1.5.1

Test code

var window = Ti.UI.createWindow({
    modal: true,    // If this line is deleted, keyboardToolbar is displayed. 
    title: 'window',
    backgroundColor: '#fff'
});
var trash = Ti.UI.createButton({
    systemButton: Ti.UI.iPhone.SystemButton.TRASH
});
var textarea = Ti.UI.createTextArea({
    editable: true,
    borderWidth: 1,
    keyboardToolbar: [trash]
});
window.add(textarea);
window.addEventListener('open', function () {
    textarea.focus();
});
window.open();