error 502 or new cloned site or existing sites

[LandiLuca]

I've installed the plugin and duplicate a 'simple site' and it seems to works.
But when I try to login in admin on the new site (or existing sites, no on network admin) I've 502 error!
I've deactiveted all plugins, but it's your plugin that cause the 502 error.
I've put this code
if (!is_main_site(get_current_blog_id())){ return; }
in multisite-clone-duplicator.php on line 20, and now the error disappears and I can login in admin area of each site!
Is this fix ok?

I've cloned a new site, after this fix, and it seems to be ok!
Let me know if it's a right fix.

(The wordpres MU is in docker with nginx)