Fix crash in ShowBookmarkBubble.

chrome/browser/ui/views/toolbar/toolbar_view.cc

 // Copyright 2013 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.
 
 #include "chrome/browser/ui/views/toolbar/toolbar_view.h"
 
 #include <algorithm>
 
 #include "base/command_line.h"
 #include "base/i18n/number_formatting.h"
@@ skipping 287 matching lines @@
       anchor_view = star_view;
     else
       anchor_view = app_menu_button_;
   }
 
   std::unique_ptr<BubbleSyncPromoDelegate> delegate;
   delegate.reset(new BookmarkBubbleSignInDelegate(browser_));
   views::Widget* bubble_widget = BookmarkBubbleView::ShowBubble(
       anchor_view, gfx::Rect(), nullptr, observer, std::move(delegate),
       browser_->profile(), url, already_bookmarked);
-  if (star_view)
+  if (bubble_widget && star_view)
     bubble_widget->AddObserver(star_view);
 }
 
 views::View* ToolbarView::GetSaveCreditCardBubbleAnchor() {
   views::View* save_credit_card_icon_view =
       location_bar()->save_credit_card_icon_view();
   return (save_credit_card_icon_view && save_credit_card_icon_view->visible())
              ? save_credit_card_icon_view
              : app_menu_button_;
 }
@@ skipping 438 matching lines @@
   if (OutdatedUpgradeBubbleView::IsAvailable()) {
     OutdatedUpgradeBubbleView::ShowBubble(app_menu_button_, browser_,
                                           auto_update_enabled);
   }
 }
 
 void ToolbarView::OnShowHomeButtonChanged() {
   Layout();
   SchedulePaint();
 }