Fix crash occurring during infobar dismissal at BVC deletion.

ios/chrome/browser/infobars/infobar_container_ios.mm

Index: ios/chrome/browser/infobars/infobar_container_ios.mm
diff --git a/ios/chrome/browser/infobars/infobar_container_ios.mm b/ios/chrome/browser/infobars/infobar_container_ios.mm
index bd1223b3784b882b6b0b16165258afddd5027418..2919449b6e254c72f296c0731fd7d8b28fde020b 100644
--- a/ios/chrome/browser/infobars/infobar_container_ios.mm
+++ b/ios/chrome/browser/infobars/infobar_container_ios.mm
@@ -22,6 +22,7 @@ InfoBarContainerIOS::InfoBarContainerIOS(
 }
 
 InfoBarContainerIOS::~InfoBarContainerIOS() {
+  delegate_ = nullptr;
   RemoveAllInfoBarsForDestruction();
 }
 
@@ -44,7 +45,7 @@ void InfoBarContainerIOS::PlatformSpecificRemoveInfoBar(
   // 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