[CHORES] Handle when result is null

lib/utils/custom_kegiatan_terdekat_button.dart

@@ -32,7 +32,8 @@ class _KegiatanTerdekatButtonState extends State<KegiatanTerdekatButton> {
         'name',
       ],
     );
-    return details.result.name;
+    final result = details.result;
+    return result == null ? 'INVALID' : result.name;
   }
 
   void _navigateToDetailPostKegiatanPage(BuildContext context) async {