Can’t take user ID

Hi all,
I’m trying to modify a plugin, so that I could make a list of the authors in my blog (even those, who have not posted), plus a thumbnail picture of them and a link to their profile. But I have the following problem: when the list appears at the page, all of the links are https://www.site.com/?author=0 … I can’t find a way to change the 0 ??

I think the problem is in this line

<?php ‘ID) . ‘” title=”‘ . sprintf(__(“Posts by %s”), attribute_escape($author->display_name)) . ‘”>’ . $name . ‘‘; ?>

and especially in the content of ($author->ID) … but whatever I try, I can’t get the 0 replaced by the real number… I would appreciate ant help!