Fix crash in DownloadsDOMHandler::GetDownloadByValue

chrome/browser/ui/webui/downloads_dom_handler.cc

 // Copyright (c) 2012 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/webui/downloads_dom_handler.h"
 
 #include <algorithm>
 #include <functional>
 
 #include "base/basictypes.h"
@@ skipping 496 matching lines @@
   CountDownloadsDOMEvents(DOWNLOADS_DOM_EVENT_SAVE_DANGEROUS);
   item->DangerousDownloadValidated();
 }
 
 content::DownloadItem* DownloadsDOMHandler::GetDownloadByValue(
     const base::ListValue* args) {
   int id = -1;
   if (!ExtractIntegerValue(args, &id))
     return NULL;
   content::DownloadItem* download_item = download_manager_->GetDownload(id);
-  if (download_item == NULL)
+  if (!download_item && original_profile_download_manager_)
     download_item = original_profile_download_manager_->GetDownload(id);
   return download_item;
 }
 
 content::WebContents* DownloadsDOMHandler::GetWebUIWebContents() {
   return web_ui()->GetWebContents();
 }
 
 void DownloadsDOMHandler::CallDownloadsList(const base::ListValue& downloads) {
   web_ui()->CallJavascriptFunction("downloadsList", downloads);
 }
 
 void DownloadsDOMHandler::CallDownloadUpdated(
     const base::ListValue& download_item) {
   web_ui()->CallJavascriptFunction("downloadUpdated", download_item);
 }