After uninstall, remove last item in Launcher folder

ui/app_list/views/app_list_main_view.cc

Index: ui/app_list/views/app_list_main_view.cc
diff --git a/ui/app_list/views/app_list_main_view.cc b/ui/app_list/views/app_list_main_view.cc
index dceae0faa72d4f49bddc4e827b990d5bc0c64783..852d480a6c9b5b1e3c811fc91379099f1cc2c5bd 100644
--- a/ui/app_list/views/app_list_main_view.cc
+++ b/ui/app_list/views/app_list_main_view.cc
@@ -266,6 +266,22 @@ void AppListMainView::UpdateCustomLauncherPageVisibility() {
   }
 }
 
+// If |folder_id| is open, this will remove AppItemList from the folder's
+// AppsGridView before the folder is deleted.
+void AppListMainView::OnSingleItemFolderWillBeDeleted(
+    const std::string& folder_id) {
+  AppListFolderView* folder_view =
+      contents_view_->apps_container_view()->app_list_folder_view();
+  AppListFolderItem* open_folder_item = folder_view->folder_item();
+
+  if (open_folder_item && open_folder_item->id() == folder_id &&
+      contents_view_->apps_container_view()->IsInFolderView()) {
+    AppsGridView* folder_grid_view = folder_view->items_grid_view();
+    if (folder_grid_view)
+      folder_grid_view->SetItemList(nullptr);  // removes observer
+  }
+}
+
 void AppListMainView::OnCustomLauncherPageEnabledStateChanged(bool enabled) {
   views::View* custom_page = contents_view_->custom_page_view();
   if (!custom_page)