Error in admin

Hi,
installed the plugin, i retrieve the following warning in admin in every taxonomy general page, custom and default.

Warning: call_user_func_array() expects parameter 1 to be a valid callback, function 'fix_visual_term_description_editor_style' not found or invalid function name in Z:\otticaincomune.locl\wp-includes\plugin.php on line 525

I would like to know if you can fix it.
Anyway, the plugin works well! I’ve rated it with 5 starts, yet.

https://www.ads-software.com/plugins/visual-term-description-editor/