SearchEngineTabHelper: avoid calling TemplateURL::GenerateFaviconURL with empty URL.

chrome/browser/ui/search_engines/search_engine_tab_helper.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/search_engines/search_engine_tab_helper.h"
 
 #include "base/memory/ptr_util.h"
 #include "base/metrics/histogram_macros.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/search_engines/template_url_fetcher_factory.h"
@@ skipping 196 matching lines @@
   data.SetKeyword(keyword);
   data.SetURL(url.spec());
   DCHECK(controller.GetLastCommittedEntry());
   const GURL& current_favicon =
       controller.GetLastCommittedEntry()->GetFavicon().url;
   // If the favicon url isn't valid, it means there really isn't a favicon, or
   // the favicon url wasn't obtained before the load started. This assumes the
   // latter.
   // TODO(sky): Need a way to set the favicon that doesn't involve generating
   // its url.
-  data.favicon_url =
-      current_favicon.is_valid()
-          ? current_favicon
-          : TemplateURL::GenerateFaviconURL(handle->GetReferrer().url);
+  if (current_favicon.is_valid()) {
+    data.favicon_url = current_favicon;
+  } else if (handle->GetReferrer().url.is_valid()) {
+    data.favicon_url =
+        TemplateURL::GenerateFaviconURL(handle->GetReferrer().url);
+  }
   data.safe_for_autoreplace = true;
   data.input_encodings.push_back(handle->GetSearchableFormEncoding());
   url_service->Add(base::MakeUnique<TemplateURL>(data));
 }