Getting this message on page when going to login to admin

When I go to my admin login page for the website https://halloweenantics.com this message shows up 4 times like this across the top of the page.
Notice: Trying to get property of non-object in /home2/toyourhe/domains/halloweenantics.com/public_html/wp-content/plugins/wp-clean-up-optimizer/wp-cleanup-optimizer.php on line 576

Notice: Trying to get property of non-object in /home2/toyourhe/domains/halloweenantics.com/public_html/wp-content/plugins/wp-clean-up-optimizer/wp-cleanup-optimizer.php on line 576

Notice: Trying to get property of non-object in /home2/toyourhe/domains/halloweenantics.com/public_html/wp-content/plugins/wp-clean-up-optimizer/wp-cleanup-optimizer.php on line 576

Notice: Trying to get property of non-object in /home2/toyourhe/domains/halloweenantics.com/public_html/wp-content/plugins/wp-clean-up-optimizer/wp-cleanup-optimizer.php on line 576

It doesn’t appear to be causing a problem with the plugin because I can use it and it is working. I am getting another message however in the admin area that is possibly releated to this but I don’t know if that is a fact or not. Here is that message:

Notice: has_cap was called with an argument that is deprecated since version 2.0.0! Usage of user levels is deprecated. Use capabilities instead. in /home2/toyourhe/domains/halloweenantics.com/public_html/wp-includes/functions.php on line 4865
I am looking for help to get rid of the first message and if the second message is related to that then also the second message. Thank you.

The page I need help with: [log in to see the link]