screen-options.php issue

In screen-options.php first there is check:
if ( !class_exists('wsScreenOptions12') )
but then class wsScreenOptions13 is added.

https://plugins.svn.wordpress.org/broken-link-checker/trunk/includes/screen-options/screen-options.php

BTW, is screen-options.php your work? May it be used by other plugins?

https://wordpress.org/plugins/broken-link-checker/