Can′t delete users when guest authors are disabled

Hi,

I’m trying to delete a user, but get a fatal php error:

PHP Fatal error: Call to a member function get_guest_author_by() on null in /wp-content/plugins/co-authors-plus/co-authors-plus.php on line 943

The guest author functionality is disabled on the site with the following filter:

add_filter( ‘coauthors_guest_authors_enabled’, ‘__return_false’ );

It works fine if I activate the guest author functionality.

Thanks,
Erlend