Filters are for modifying data that's passed through them. You need to take the input, modify it, then `return` it.

    function exclude_not_allowed_terms( $args ) {
        if(!current_user_can('edit_others_posts')) {
            $args['meta_query'] = array(
                array(
                    'key'    => 'owner',
                    'value'  => get_current_user_id()
                )
            );
        }
        return $args;
    }
    add_filter('get_terms_defaults','exclude_not_allowed_terms');