title: TabGroup within a NavGroup - Both navbars show and NavGroup title missing
body: <p>I have an app that contains a messaging system. It consists of a TableView that splits off into two TabGroups, using a NavGroup (I'm using Ti 1.7.5).</p>
  
  <p>The problem I'm seeing is two fold;</p>
  
  <ul>
  <li>Both title bars of the NavGroup and the Tab are being displayed, and</li>
  <li>The TabGroup's title is not being displayed in the NavGroup title bar.</li>
  </ul>
  
  <p>The following screenshot illustrates both problems:</p>
  
  <p><img src="https://i.stack.imgur.com/Jj8Gv.png" alt="TabGroup in a NavGroup problem"></p>
  
  <p>Code (please note this is heavily summarised):</p>
  
  <pre><code>csu.module.messages.createMainWindow = function() {
      csu.module.messages.mainWindow = Ti.UI.createWindow($$.moduleMainWindow);
      csu.module.messages.navGroupContainer = Ti.UI.createWindow($$.modalContainer);
      var mainTableView = Ti.UI.createTableView($$.tableView);
  
      csu.module.messages.navGroup = Ti.UI.iPhone.createNavigationGroup({
          window: csu.module.messages.mainWindow
      }); 
  
      ...
  
      mainTableView.addEventListener('click', function(e){
          // Event info
          var index = e.index, section = e.section, row = e.row, rowData = e.rowData;
  
          switch(index) {
              case 0:
                  // inbox;
                  csu.module.messages.inboxView = csu.module.messages.createInboxView(); // returns the tabgroup
                  csu.module.messages.navGroup.open(csu.module.messages.inboxView);
                  break;
              case 1:
                  // archive;
                  csu.module.messages.archiveView = csu.module.messages.createArchiveView(); // Returns another tabgroup
                  csu.module.messages.navGroup.open(csu.module.messages.archiveView);
                  break;
          }
      });
  
      ...
  
      csu.module.messages.mainWindow.add(mainTableView);
      csu.module.messages.navGroupContainer.add(csu.module.messages.navGroup);
  }
  
  csu.module.messages.createInboxView = function() {
      var tabGroup = Ti.UI.createTabGroup({
          title: 'Inbox',
          navBarHidden: false,
          backgroundColor: '#000000',
          barColor: csu.ui.theme.headerColor // black
      });
  
      var criticalInbox = csu.module.messages.createListWindow(m_Config.MESSAGE_TYPE_CRITICAL, true);
  
      csu.module.messages.criticalInboxTab = Ti.UI.createTab({
          title: 'Critical',
          icon: 'images/tab-critical.png',
          window: criticalInbox
      });
  
      ...
  
      // two other tabs are created
  
      tabGroup.addTab(csu.module.messages.criticalInboxTab);
      tabGroup.addTab(csu.module.messages.importantInboxTab);
      tabGroup.addTab(csu.module.messages.generalInboxTab);
  
      return tabGroup;
  };
  
  csu.module.messages.createListWindow = function(listType, isInbox) {
      var tabWindow, title, tableView;
  
      switch(listType) {
          case m_Config.MESSAGE_TYPE_CRITICAL:
              title = 'Critical';
              break;
          case m_Config.MESSAGE_TYPE_IMPORTANT:
              title = 'Important';
              break;
          case m_Config.MESSAGE_TYPE_GENERAL:
              title = 'General';
              break;
      };
  
      tableView = Ti.UI.createTableView();
      var tableData = new Array();
      tableView.setData(tableData);
  
      tabWindow = Ti.UI.createWindow({
          title: title,
          navBarHidden: false         
      });
  
      tabWindow.add(tableView);
  
      return tabWindow;
  }
  </code></pre>
  
  <p>Does anyone know of a work around or something to get the title in the Navigation bar from the TabGroup? Is this a bug?</p>
  
  <p>Your assistance is appreciated.</p>