Check that the newly installed PWA exists before dereferencing it.

Bug: 976384
Change-Id: Ibb18e97bd5e799a513922b81698eb5cea98b5bfc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1665912
Commit-Queue: Jon Mann <jonmann@chromium.org>
Reviewed-by: Kyle Horimoto <khorimoto@chromium.org>
Cr-Commit-Position: refs/heads/master@{#670284}

chrome/browser/chromeos/android_sms/android_sms_app_manager_impl.cc

@@ -159,11 +159,8 @@ void AndroidSmsAppManagerImpl::OnSetUpNewAppResult(
   const extensions::Extension* new_pwa = setup_controller_->GetPwa(
       GetAndroidMessagesURL(true /* use_install_url */));
 
-  // If the installation succeeded, a PWA should exist at the new URL.
-  DCHECK_EQ(success, new_pwa != nullptr);
-
-  // If the app failed to install, it should no longer be launched.
-  if (!success) {
+  // If the app failed to install or the PWA does not exist, do not launch.
+  if (!success || !new_pwa) {
     is_app_launch_pending_ = false;
     return;
   }