Fix crash on FavoritesObserver (#5335)

Task/Issue URL: https://app.asana.com/0/1202552961248957/1208841273777750/f

### Description
Fix NPE when trying to get `AppWidgetManager.getInstance`

### Steps to test this PR
NA, code review

Author: aitorvs

app/src/main/java/com/duckduckgo/app/widget/FavoritesObserver.kt

@@ -20,34 +20,36 @@ import android.appwidget.AppWidgetManager
 import android.content.ComponentName
 import android.content.Context
 import androidx.lifecycle.LifecycleOwner
+import androidx.lifecycle.coroutineScope
 import com.duckduckgo.app.browser.R
-import com.duckduckgo.app.di.AppCoroutineScope
 import com.duckduckgo.app.lifecycle.MainProcessLifecycleObserver
 import com.duckduckgo.common.utils.DispatcherProvider
 import com.duckduckgo.di.scopes.AppScope
 import com.duckduckgo.savedsites.api.SavedSitesRepository
 import com.duckduckgo.widget.SearchAndFavoritesWidget
 import dagger.SingleInstanceIn
 import javax.inject.Inject
-import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.launch
 
 @SingleInstanceIn(AppScope::class)
 class FavoritesObserver @Inject constructor(
     context: Context,
     private val savedSitesRepository: SavedSitesRepository,
-    @AppCoroutineScope private val appCoroutineScope: CoroutineScope,
     private val dispatcherProvider: DispatcherProvider,
 ) : MainProcessLifecycleObserver {
 
-    private val instance = AppWidgetManager.getInstance(context)
+    private val appWidgetManager: AppWidgetManager? by lazy {
+        AppWidgetManager.getInstance(context)
+    }
     private val componentName = ComponentName(context, SearchAndFavoritesWidget::class.java)
 
     override fun onStart(owner: LifecycleOwner) {
-        appCoroutineScope.launch(dispatcherProvider.io()) {
-            savedSitesRepository.getFavorites().collect {
-                instance.notifyAppWidgetViewDataChanged(instance.getAppWidgetIds(componentName), R.id.favoritesGrid)
-                instance.notifyAppWidgetViewDataChanged(instance.getAppWidgetIds(componentName), R.id.emptyfavoritesGrid)
+        owner.lifecycle.coroutineScope.launch(dispatcherProvider.io()) {
+            appWidgetManager?.let { instance ->
+                savedSitesRepository.getFavorites().collect {
+                    instance.notifyAppWidgetViewDataChanged(instance.getAppWidgetIds(componentName), R.id.favoritesGrid)
+                    instance.notifyAppWidgetViewDataChanged(instance.getAppWidgetIds(componentName), R.id.emptyfavoritesGrid)
+                }
             }
         }
     }