This is a bug. The function does not check if a posts page has been configured in the WordPress “Reading Settings”.
Replace /wp-content/plugins/breadcrumbs/yoast-breadcrumbs.php, line 213 from this:
$bloglink = $homelink.' '.$opt['sep'].' <a href="'.get_permalink(get_option('page_for_posts')).'">'.$opt['blog'].'</a>';
to this:
$bloglink = $homelink;
if ( $page_for_posts = get_option('page_for_posts') )
$bloglink .= ' '.$opt['sep'].' <a href="'.get_permalink($page_for_posts).'">'.$opt['blog'].'</a>';
I’d like to add a patch file but it doesn’t seem to be possible to add attachments here…