Prevent access to keyword table if it has not yet been instantiated.

This change aims at addressing a null pointer dereferences when the
Chrome is run for the first time on Android.

Change-Id: I59493cc673e51a95673288f60180bc01f46c566d
Fixed: 1405309
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4189311
Reviewed-by: Peter Williamson <petewil@chromium.org>
Reviewed-by: Justin Donnelly <jdonnelly@chromium.org>
Auto-Submit: Tomasz Wiszkowski <ender@google.com>
Commit-Queue: Peter Williamson <petewil@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1096515}

components/search_engines/keyword_web_data_service.cc

@@ -26,8 +26,9 @@ WebDatabase::State PerformKeywordOperationsImpl(
 std::unique_ptr<WDTypedResult> GetKeywordsImpl(WebDatabase* db) {
   KeywordTable* const keyword_table = KeywordTable::FromWebDatabase(db);
   WDKeywordsResult result;
-  if (!keyword_table->GetKeywords(&result.keywords))
+  if (!keyword_table || !keyword_table->GetKeywords(&result.keywords)) {
     return nullptr;
+  }
 
   result.default_search_provider_id =
       keyword_table->GetDefaultSearchProviderID();