I also get this error whenever trying to use the WP CLI while this plugin is activated on my site.
I also get this notice:
Notice: Use of undefined constant AUTOSAVE_INTERVAL – assumed ‘AUTOSAVE_INTERVAL’ in /Users/andrewmiller/Sites/bcen/wp-includes/script-loader.php on line 1086
The fatal error only occurs while the plugin is active on the site.
I am thinking that maybe it has something to do with when the plugin is initialized?
