AJAX error on Autocomplete Username when writing a new private message on IE or Chrome or Recoverable fatal error: Method Databa

Log: Recoverable fatal error: Method DatabaseCondition::__toString() must return a string value in privatemsg_realname_query_privatemsg_autocomplete_alter() (line 60 of sites/all/modules/privatemsg/privatemsg_realname/privatemsg_realname.module).
That cause AJAX error on Autocomplete Username when writing a new private message on IE or Chrome (Firefox is OK) in
function privatemsg_realname_query_privatemsg_autocomplete_alter(SelectQueryInterface $query) {}
if ($condition['field'] == 'u.name') {

should be change to

 if (isset($condition['field']) && is_string($condition['field'])
                && $condition['field'] == 'u.name') {

to fix this Error.