[Plugin: WordPress Backup] Broken bad!!!

I tried to install this plugin.

The minute I did, I got this error message and could NOT even load WP-ADMIN:

Fatal error: Call to undefined function wp_get_current_user() in …./wp-includes/capabilities.php on line 1059.

Was in a panic, until I followed the advice on this excellent page:
https://www.zoofusion.com.au/studio537/wordpress/quickfix-fatal-error-call-to-undefined-function-wp_get_current_user