Reload with empty navigation manager should not crash

ios/web/navigation/navigation_manager_impl.mm

 // 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.
 
 #import "ios/web/navigation/navigation_manager_impl.h"
 
 #include <stddef.h>
 
 #include <utility>
 
@@ skipping 321 matching lines @@
 NavigationItemList NavigationManagerImpl::GetBackwardItems() const {
   return [session_controller_ backwardItems];
 }
 
 NavigationItemList NavigationManagerImpl::GetForwardItems() const {
   return [session_controller_ forwardItems];
 }
 
 void NavigationManagerImpl::Reload(ReloadType reload_type,
                                    bool check_for_reposts) {
+  if (!GetTransientItem() && !GetPendingItem() && !GetLastCommittedItem())
+    return;
+
   delegate_->Reload();
 }
 
 void NavigationManagerImpl::CopyStateFromAndPrune(
     const NavigationManager* manager) {
   DCHECK(manager);
   CRWSessionController* other_session =
       static_cast<const NavigationManagerImpl*>(manager)->session_controller_;
   [session_controller_ copyStateFromSessionControllerAndPrune:other_session];
 }
@@ skipping 97 matching lines @@
   const ScopedNavigationItemImplList& items = [session_controller_ items];
   while (index >= 0) {
     NavigationItem* item = items[index--].get();
     if (!client->IsAppSpecificURL(item->GetVirtualURL()))
       return item;
   }
   return nullptr;
 }
 
 }  // namespace web