iwa: Check for null WebAppProvider in ChromeBrowsingDataModelDelegate

This is a speculative fix based on the stack trace in the crash
report. WebAppProvider can be null on ChromeOS in certain cases, which
will be changed/fixed soon, but this will handle the null case in
the meantime.

Bug: 1427992, 1311065
Change-Id: If5dfca0194764f2e1f738a9c424c0b8bee624ff4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4383196
Reviewed-by: Joshua Bell <jsbell@chromium.org>
Commit-Queue: Robbie McElrath <rmcelrath@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1123907}

chrome/browser/browsing_data/chrome_browsing_data_model_delegate.cc

@@ -75,9 +75,8 @@ ChromeBrowsingDataModelDelegate::~ChromeBrowsingDataModelDelegate() = default;
 void ChromeBrowsingDataModelDelegate::GetAllDataKeys(
     base::OnceCallback<void(std::vector<DelegateEntry>)> callback) {
 #if !BUILDFLAG(IS_ANDROID)
-  if (storage_partition_->GetConfig().is_default()) {
-    auto* web_app_provider = web_app::WebAppProvider::GetForWebApps(profile_);
-    DCHECK(web_app_provider);
+  auto* web_app_provider = web_app::WebAppProvider::GetForWebApps(profile_);
+  if (web_app_provider && storage_partition_->GetConfig().is_default()) {
     web_app_provider->scheduler().GetIsolatedWebAppBrowsingData(
         base::BindOnce(&IsolatedWebAppBrowsingDataToDelegateEntries)
             .Then(std::move(callback)));