wp_get_attachment_image_src returns incorrect URL on multisite

I found this stray code in the header.php

$GLOBALS[blog_id] = get_option('woo_blog_id');

This wiped out the global variable that get_current_blog_id() relies on to get the site id in multisite. This is then used by wp_get_attachment_url() to build the appropriate URL.

Because I was getting an incorrect site id, my attachment URLs were coming out wrong.