             
             if (targetNavigator is TabbedViewNavigator)
             {
-                TabbedViewNavigator(targetNavigator).tabBar.includeInLayout = 
-                    explicitIncludeInLayout;
+                var tabBar:ButtonBarBase = TabbedViewNavigator(targetNavigator).tabBar;
+                
+                if (tabBar)
+                    tabBar.includeInLayout = explicitIncludeInLayout;
             }
             else if (targetNavigator is ViewNavigator)
             {
-                ViewNavigator(targetNavigator).actionBar.includeInLayout = 
-                    explicitIncludeInLayout;
+                if (actionBar)
+                    actionBar.includeInLayout = explicitIncludeInLayout;
             }
         }
         else

            if (actionBar && actionBar.titleDisplay
                && (actionBar.titleDisplay is DisplayObject)
                && DisplayObject(actionBar.titleDisplay).visible)
                DisplayObject(actionBar.titleDisplay).cacheAsBitmap = false;
            
            if (cachedTitleGroup)
                removeComponentFromContainerSkin(cachedTitleGroup, actionBar.skin);

            
            if (targetNavigator is TabbedViewNavigator)
            {
                var tabBar:ButtonBarBase = TabbedViewNavigator(targetNavigator).tabBar;
                
                if (tabBar)
                {
                    targets.push(tabBar);
                    explicitIncludeInLayout = tabBar.includeInLayout; 
                    tabBar.includeInLayout = false;
                }
            }
            else if (targetNavigator is ViewNavigator)
            {
                if (actionBar)
                {
                    targets.push(actionBar);
                    explicitIncludeInLayout = actionBar.includeInLayout; 
                    actionBar.includeInLayout = false;
                }
            }
            
            if (cachedNavigator)
