Fix null check to avoid RendererDidNavigateSamePage crash.

content/browser/frame_host/navigation_controller_impl.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.
 
 /*
  * Copyright (C) 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
  * Copyright (C) 2008 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved.
  *     (http://www.torchmobile.com/)
  *
@@ skipping 990 matching lines @@
     return NAVIGATION_TYPE_EXISTING_PAGE;
   }
 
   if (pending_entry_ && pending_entry_index_ == -1 &&
       pending_entry_->GetUniqueID() == params.nav_entry_id) {
     // In this case, we have a pending entry for a load of a new URL but Blink
     // didn't do a new navigation (params.did_create_new_entry). First check to
     // make sure Blink didn't treat a new cross-process navigation as inert, and
     // thus set params.did_create_new_entry to false. In that case, we must
     // treat it as NEW since the SiteInstance doesn't match the entry.
-    if (GetLastCommittedEntry() &&
+    if (!GetLastCommittedEntry() ||
         GetLastCommittedEntry()->site_instance() != rfh->GetSiteInstance())
       return NAVIGATION_TYPE_NEW_PAGE;
 
     // Otherwise, this happens when you press enter in the URL bar to reload. We
     // will create a pending entry, but Blink will convert it to a reload since
     // it's the same page and not create a new entry for it (the user doesn't
     // want to have a new back/forward entry when they do this). Therefore we
     // want to just ignore the pending entry and go back to where we were (the
     // "existing entry").
     // TODO(creis,avi): Eliminate SAME_PAGE in https://crbug.com/536102.
@@ skipping 1089 matching lines @@
     }
   }
 }
 
 void NavigationControllerImpl::SetGetTimestampCallbackForTest(
     const base::Callback<base::Time()>& get_timestamp_callback) {
   get_timestamp_callback_ = get_timestamp_callback;
 }
 
 }  // namespace content