warning at line 521 of mvb_wp_access.php

I am seeing a warning as follows:

Warning: array_merge() [function.array-merge]: Argument #1 is not an array in xxxxxx/mvb_wp_access.php on line 521

Solved by changing:
if (isset($query->query_vars[‘post__not_in’])) {
$query->query_vars[‘post__not_in’] = array_merge($query->query_vars[‘post__not_in’], $r_posts);
} else {
$query->query_vars[‘post__not_in’] = $r_posts;
}

To:
if (isset($query->query_vars[‘post__not_in’]) && is_array($query->query_vars[‘post__not_in’])) {
$query->query_vars[‘post__not_in’] = array_merge($query->query_vars[‘post__not_in’], $r_posts);
} else {
$query->query_vars[‘post__not_in’] = $r_posts;
}

https://www.ads-software.com/extend/plugins/advanced-access-manager/