Fix crash occurring during infobar dismissal at BVC deletion.

ios/chrome/browser/infobars/infobar_container_ios.mm

 // Copyright 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 "ios/chrome/browser/infobars/infobar_container_ios.h"
 
 #import <UIKit/UIKit.h>
 
 #include "base/logging.h"
 #include "base/message_loop/message_loop.h"
 #include "ios/public/provider/chrome/browser/chrome_browser_provider.h"
 #include "ios/chrome/browser/infobars/infobar.h"
 #include "ios/chrome/browser/infobars/infobar_container_view.h"
 
 InfoBarContainerIOS::InfoBarContainerIOS(
     infobars::InfoBarContainer::Delegate* delegate)
     : InfoBarContainer(delegate), delegate_(delegate) {
   DCHECK(delegate);
   container_view_.reset([[InfoBarContainerView alloc] init]);
   [container_view_ setAutoresizingMask:UIViewAutoresizingFlexibleWidth |
                                        UIViewAutoresizingFlexibleTopMargin];
 }
 
 InfoBarContainerIOS::~InfoBarContainerIOS() {
+  delegate_ = nullptr;
   RemoveAllInfoBarsForDestruction();
 }
 
 InfoBarContainerView* InfoBarContainerIOS::view() {
   return container_view_;
 }
 
 void InfoBarContainerIOS::PlatformSpecificAddInfoBar(infobars::InfoBar* infobar,
                                                      size_t position) {
   InfoBarIOS* infobar_ios = static_cast<InfoBarIOS*>(infobar);
   [container_view_ addInfoBar:infobar_ios position:position];
 }
 
 void InfoBarContainerIOS::PlatformSpecificRemoveInfoBar(
     infobars::InfoBar* infobar) {
   InfoBarIOS* infobar_ios = static_cast<InfoBarIOS*>(infobar);
   infobar_ios->RemoveView();
   // If total_height() is 0, then the infobar was removed after an animation. In
   // this case, signal the delegate that the state changed.
   // Otherwise, the infobar is being replaced by another one. Do not call the
   // delegate in this case, as the delegate will be updated when the new infobar
   // is added.
-  if (infobar->total_height() == 0)
+  if (infobar->total_height() == 0 && delegate_)
     delegate_->InfoBarContainerStateChanged(false);
 
   // TODO(rohitrao, jif): [Merge 239355] Upstream InfoBarContainer deletes the
   // infobar. Avoid deleting it here.
   // crbug.com/327290
   // base::MessageLoop::current()->DeleteSoon(FROM_HERE, infobar_ios);
 }
 
 void InfoBarContainerIOS::PlatformSpecificInfoBarStateChanged(
     bool is_animating) {
   [container_view_ setUserInteractionEnabled:!is_animating];
   [container_view_ setNeedsLayout];
 }
 
 void InfoBarContainerIOS::SuspendInfobars() {
   ios::GetChromeBrowserProvider()->SetUIViewAlphaWithAnimation(container_view_,
                                                                0);
 }
 
 void InfoBarContainerIOS::RestoreInfobars() {
   ios::GetChromeBrowserProvider()->SetUIViewAlphaWithAnimation(container_view_,
                                                                1);
 }