Fix UniversalBGTask crash and gracefully handle CoCreateInstance failures

dev/WindowsAppRuntime_UniversalBGTaskDLL/Task.cpp

@@ -20,9 +20,45 @@ namespace winrt::Microsoft::Windows::ApplicationModel::Background::UniversalBGTa
         ApplicationDataContainer localSettings = ApplicationData::Current().LocalSettings();
         auto values = localSettings.Values();
         auto lookupobj = values.Lookup(lookupStr);
+
+        // LocalSettings.Lookup returns S_OK with a null IInspectable when the key is missing.
+        // Treat this as an orphaned OS task registration: log and unregister so the broker
+        // stops re-firing it. Returning cleanly is preferred over throwing because thrown
+        // exceptions are treated as transient by the broker and would be retried indefinitely.
+        if (!lookupobj)
+        {
+            LOG_HR_MSG(
+                HRESULT_FROM_WIN32(ERROR_NOT_FOUND),
+                "UniversalBGTask: no CLSID stored in LocalSettings for TaskId='%ls'. Unregistering orphaned task.",
+                lookupStr.c_str());
+            try
+            {
+                taskInstance.Task().Unregister(true);
+            }
+            CATCH_LOG_MSG("UniversalBGTask: failed to unregister orphaned task TaskId='%ls'.", lookupStr.c_str());
+            return;
+        }
+
         winrt::guid comClsId = winrt::unbox_value<winrt::guid>(lookupobj);
 
-        THROW_IF_FAILED(CoCreateInstance(comClsId, nullptr, CLSCTX_LOCAL_SERVER, winrt::guid_of<winrt::Windows::ApplicationModel::Background::IBackgroundTask>(), winrt::put_abi(m_bgTask)));
+        // CoCreateInstance can fail when the COM class isn't registered, the stored CLSID is
+        // GUID_NULL, or the impl doesn't expose IBackgroundTask. Log the HR with the CLSID
+        // for diagnostics and return; do not unregister, since the failure may be transient.
+        wchar_t comClsIdStr[40]{};
+        ::StringFromGUID2(comClsId, comClsIdStr, ARRAYSIZE(comClsIdStr));
+        HRESULT coCreateHr = CoCreateInstance(comClsId, nullptr, CLSCTX_LOCAL_SERVER,
+            winrt::guid_of<winrt::Windows::ApplicationModel::Background::IBackgroundTask>(),
+            winrt::put_abi(m_bgTask));
+        if (FAILED(coCreateHr))
+        {
+            LOG_HR_MSG(
+                coCreateHr,
+                "UniversalBGTask: CoCreateInstance failed for CLSID=%ls referenced by TaskId='%ls'.",
+                comClsIdStr,
+                lookupStr.c_str());
+            return;
+        }
+
         m_bgTask.Run(taskInstance);
     }
 }