Undefined variable errors on page saves

Just started getting the following notice when saving changes to pages:

Notice: Undefined variable: protocol in /home/dhmreale/public_html/dhmwp/wp-content/plugins/wp-super-cache/wp-cache-phase1.php on line 583

Looking at wp-cache-phase1.php I don’t see $protocol declared anywhere in the file.

wp_cache_debug( “get_current_url_supercache_dir: Removing SERVER_NAME ({$WPSC_HTTP_HOST}) and $protocol from permalink ($permalink). Is the url right?”, 1 );

Any idea what’s going on?

https://ww.wp.xz.cn/plugins/wp-super-cache/