Where are you writing this script? You initial glide record appears to be querying for a sys_id but passing in the record number, if you're on the request item form and looking to get all child requests then the query will look like this:

var value = new GlideRecord('sc_task');
value.addQuery('request_item', current.getUniqueValue());
value.query();
gs.log('this query as returned ' + value.getRowCount() + ' records');
while (value.next()) {
//rest of your code
}

The gs.log will log to the script log statements module so you can check any debugging lines there.