Wishlist WP Site Fatal Error

Hello, I’d like to ask help on fixing this fatal error on my client’s WP site:

Fatal error: Call-time pass-by-reference has been removed in public_html/wp-content/plugins/wishlist-member/core/Class.php(48) : eval()’d code(3) : eval()’d code on line 31

The site is antiagingbusinesssystems.com.

I’ve Googled a previous thread that it was caused by malware, but they weren’t able to provide a solution.

Can anyone look on this please.