DPWA: handle null app case during GetShortcutInfoForApp

App could be a null pointer if registry profile is being deleted.
In this case, we will not attempt to get shortcut info.

Bug: 1113276
Change-Id: I0ff77b56d701e54350763c1fbabd4f43a0c85f4b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2388892Reviewed-by: Daniel Murphy <dmurph@chromium.org>
Reviewed-by: Alexey Baskakov <loyso@chromium.org>
Commit-Queue: Phillis Tang <phillis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#805438}

chrome/browser/web_applications/web_app_shortcut_manager.cc

@@ -47,7 +47,12 @@ void WebAppShortcutManager::GetShortcutInfoForApp(
     const AppId& app_id,
     GetShortcutInfoCallback callback) {
   const WebApp* app = GetWebAppRegistrar().GetAppById(app_id);
-  DCHECK(app);
+
+  // app could be nullptr if registry profile is being deleted.
+  if (!app) {
+    std::move(callback).Run(nullptr);
+    return;
+  }
 
   // Build a common intersection between desired and downloaded icons.
   auto icon_sizes_in_px = base::STLSetIntersection<std::vector<SquareSizePx>>(