Fix SEGV in ErrorScreenHandler::HandleHideCaptivePortal.

chrome/browser/ui/webui/chromeos/login/error_screen_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/chromeos/login/error_screen_handler.h"
 
 #include "base/message_loop/message_loop.h"
 #include "base/time/time.h"
 #include "chrome/browser/chromeos/login/screens/network_error_model.h"
 #include "chrome/grit/chromium_strings.h"
@@ skipping 58 matching lines @@
 bool ErrorScreenHandler::GetScreenName(OobeUI::Screen screen,
                                        std::string* name) const {
   OobeUI* oobe_ui = static_cast<OobeUI*>(web_ui()->GetController());
   if (!oobe_ui)
     return false;
   *name = oobe_ui->GetScreenName(screen);
   return true;
 }
 
 void ErrorScreenHandler::HandleHideCaptivePortal() {
-  model_->HideCaptivePortal();
+  if (model_)
+    model_->HideCaptivePortal();
 }
 
 void ErrorScreenHandler::RegisterMessages() {
   AddCallback("hideCaptivePortal",
               &ErrorScreenHandler::HandleHideCaptivePortal);
   BaseScreenHandler::RegisterMessages();
 }
 
 void ErrorScreenHandler::DeclareLocalizedValues(
     ::login::LocalizedValuesBuilder* builder) {
@@ skipping 36 matching lines @@
     return;
 
   if (show_on_init_) {
     // TODO(nkostylev): Check that context initial state is properly passed.
     Show();
     show_on_init_ = false;
   }
 }
 
 }  // namespace chromeos