[M118] OOBE: Fix ErrorScreen::ShowImpl() crash

Check that `LoginDisplayHost::default_host()` does not return null
before accessing `LoginDisplayHost::default_host()->HasUserPods()`.

If `LoginDisplayHost::default_host()` returns null, it will be
assumed that the error is not closeable, similar to the behavior
before https://crrev.com/c/4720650 was landed.

(cherry picked from commit 6ba7237)

Bug: b:302369390
Change-Id: I4c450ee6a3673092bb307997ba323c586fe87941
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4898537
Commit-Queue: Danila Kuzmin <dkuzmin@google.com>
Auto-Submit: Osama Fathy <osamafathy@google.com>
Reviewed-by: Danila Kuzmin <dkuzmin@google.com>
Cr-Original-Commit-Position: refs/heads/main@{#1202394}
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4902243
Commit-Queue: Osama Fathy <osamafathy@google.com>
Cr-Commit-Position: refs/branch-heads/5993@{#957}
Cr-Branched-From: 5113507-refs/heads/main@{#1192594}

chrome/browser/ash/login/screens/error_screen.cc

@@ -260,8 +260,9 @@ void ErrorScreen::ShowImpl() {
     return;
   }
 
-  const bool is_closeable =
-      LoginDisplayHost::default_host()->HasUserPods() && !is_persistent_;
+  const bool is_closeable = LoginDisplayHost::default_host() &&
+                            LoginDisplayHost::default_host()->HasUserPods() &&
+                            !is_persistent_;
   view_->ShowScreenWithParam(is_closeable);
   LOG(WARNING) << "Network error screen message is shown";
   NetworkHandler::Get()->network_state_handler()->RequestPortalDetection();