Multiple PHP Notice Warnings

Hello,
having the WP_DEBUG constant set to true in my development environment, in the downloads page I get a bunch of PHP notice warnings which should be easy to fix. There are other warnings on admin as well. Nice plugin, but please fix these warnings.

Notice: Undefined index: dl_cat in wp-downloadmanager\wp-downloadmanager.php on line 506

Notice: Undefined index: dl_page in wp-downloadmanager\wp-downloadmanager.php on line 507

Notice: Undefined index: dl_search in wp-downloadmanager\wp-downloadmanager.php on line 508

https://ww.wp.xz.cn/plugins/wp-downloadmanager/