added code improvement

app/controllers/calendar/calendar.php

@@ -12,8 +12,12 @@ class Calendar_CalendarController extends AuthenticatedController
     }
 
 
-    protected function buildSidebar($schedule = false, $user_id = '', $group_id = '')
-    {
+    protected function buildSidebar(
+        bool $schedule = false,
+        string $user_id = '',
+        string $group_id = ''
+    ) {
+
         $sidebar = Sidebar::get();
 
         $actions = new ActionsWidget();