Here's a robust way of going through groups to find the right one:

answer = findApprovingManager();

function findApprovingManager() {
    if (current.assignment_group.u_organizational_type == 'division') {
        answer.push(current.assignment_group.manager.toString()); // Base Case
    } else {
        answer.push(grabHierarchy(current.assignment_group.parent.toString()));
    }
    return answer;
}

function grabManager(selectedGrp) {

    var result = [];

    var divGrp = new GlideRecord('sys_user_group');
    divGrp.addQuery('sys_id', selectedGrp.toString());
    divGrp.addQuery('u_organizational_type', 'division');
    divGrp.addActiveQuery();
    divGrp.query();

    if (!divGrp.next()) {
        var gr = new GlideRecord('sys_user_group');
        gr.addQuery('sys_id', selectedGrp.toString());
        gr.query();
        if (gr.next()) {
            var nextGrp = gr.parent;
            grabManager(nextGrp);
        }
    } else {
        result.push(divGrp.manager);
    }
    return result;
}

Let me know if this answers your question by marking it as correct.