Upgrade warning

I’ve just upgraded from 3.1.6. to 3.1.7 by deleting the plugin’s directory and unpacking the new (much smaller) ZIP. Saw this in the web server log:

PHP Warning: call_user_func_array() expects parameter 1 to be a valid callback, class 'CMTooltipGlossaryShared' does not have a method 'cmtt_warn_on_upgrade' in /var/www/wordpress/wp-includes/plugin.php on line 496" while reading upstream

https://wordpress.org/plugins/enhanced-tooltipglossary/