Fix a crash due to the modal signin being closed before being shown.

chrome/browser/ui/views/profiles/signin_view_controller_delegate_views.cc

 // Copyright 2016 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/views/profiles/signin_view_controller_delegate_views.h"
 
 #include "base/macros.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/profiles/profile_avatar_icon_util.h"
 #include "chrome/browser/signin/signin_promo.h"
@@ skipping 56 matching lines @@
 
 bool SigninViewControllerDelegateViews::ShouldShowCloseButton() const {
   return false;
 }
 
 int SigninViewControllerDelegateViews::GetDialogButtons() const {
   return ui::DIALOG_BUTTON_NONE;
 }
 
 void SigninViewControllerDelegateViews::PerformClose() {
-  modal_signin_widget_->Close();
+  if (modal_signin_widget_)
+    modal_signin_widget_->Close();
 }
 
 void SigninViewControllerDelegateViews::ResizeNativeView(int height) {
   int max_height = browser_
       ->window()
       ->GetWebContentsModalDialogHost()
       ->GetMaximumDialogSize().height();
   content_view_->SetPreferredSize(
       gfx::Size(kModalDialogWidth, std::min(height, max_height)));
   content_view_->Layout();
@@ skipping 79 matching lines @@
 
 SigninViewControllerDelegate*
 SigninViewControllerDelegate::CreateSyncConfirmationDelegate(
     SigninViewController* signin_view_controller,
     Browser* browser) {
   return new SigninViewControllerDelegateViews(
       signin_view_controller,
       SigninViewControllerDelegateViews::CreateSyncConfirmationWebView(browser),
       browser, true);
 }