apps-menu: Handle .desktop files from non-standard directories

.desktop files in non-standard locations are not handled by GIO,
so looking up apps for entries for such locations (e.g. a
directory added via the AppsDir directive) will fail. We can
still handle this case in the menu by creating the app directly
from the entry's AppInfo.

https://bugzilla.gnome.org/show_bug.cgi?id=762206

extensions/apps-menu/extension.js

@@ -404,6 +404,8 @@ const ApplicationsButton = new Lang.Class({
                     continue;
                 }
                 let app = appSys.lookup_app(id);
+                if (!app)
+                    app = new Shell.App({ app_info: entry.get_app_info() });
                 if (app.get_app_info().should_show())
                     this.applicationsByCategory[categoryId].push(app);
             } else if (nextType == GMenu.TreeItemType.DIRECTORY) {