Have you recently updated your theme? The error doesn’t seem to relate to the plugin, but rather to your theme.
The ‘array_merge()’ function says it expects an array, which is a list of values. If it doesn’t get a list, it will give a warning. The second error is a result of the first. The server probably tries to redirect you to a different page. As an error has already been sent to your browser, it can’t send you to a different page.
You’ll need to have a look at what’s happening in your ‘admins.php’ file in your theme’s ‘library’ folder.