[ios clean] Add placeholder for NTP bookmarks, chrome home and open tabs.

ios/chrome/browser/ui/ntp/new_tab_page_toolbar_controller.mm

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #import "ios/chrome/browser/ui/ntp/new_tab_page_toolbar_controller.h"
 
 #include "base/logging.h"
 #include "base/mac/scoped_nsobject.h"
 #include "base/metrics/user_metrics.h"
 #include "base/metrics/user_metrics_action.h"
@@ skipping 188 matching lines @@
     base::scoped_nsobject<GenericChromeCommand> command(
         [[GenericChromeCommand alloc] initWithTag:IDC_SHOW_FORWARD_HISTORY]);
     [_forwardButton chromeExecuteCommand:command];
   }
 }
 
 - (void)hideViewsForNewTabPage:(BOOL)hide {
   [super hideViewsForNewTabPage:hide];
   // Show the back/forward buttons if there is forward history.
   ToolbarModelIOS* toolbarModelIOS = [_delegate toolbarModelIOS];
-  BOOL forwardEnabled = toolbarModelIOS->CanGoForward();
-  [_backButton setHidden:!forwardEnabled && hide];
-  [_backButton setEnabled:toolbarModelIOS->CanGoBack()];
-  [_forwardButton setHidden:!forwardEnabled && hide];
+  if (toolbarModelIOS) {
+    BOOL forwardEnabled = toolbarModelIOS->CanGoForward();
+    [_backButton setHidden:!forwardEnabled && hide];
+    [_backButton setEnabled:toolbarModelIOS->CanGoBack()];
+    [_forwardButton setHidden:!forwardEnabled && hide];
+  }
 }
 
 - (void)focusOmnibox:(id)sender {
   [_focuser focusFakebox];
 }
 
 - (IBAction)stackButtonTouchDown:(id)sender {
   [_delegate prepareToEnterTabSwitcher:self];
 }
 
 @end