Passing a variable as an argument to record.getFieldValues not working

Hi everybody,
I am trying to look up multiselect values in an item record using a variable as the argument and I am getting null as a result. I am trying something like this:

function getColorSizeAndOther()
{
    //Get the full list of matrix attributes (a custom record)
    var filters = new Array();
    filters[0] = new nlobjSearchFilter('isinactive',null,'is','F');
    var columns = new Array();
    columns[0] = new nlobjSearchColumn('custrecord_list_id');
    columns[1] = new nlobjSearchColumn('custrecord_attribute_type');
    var results = nlapiSearchRecord('customrecord_matrix_attribute',null,filters,columns);
       
    //Sort the size attribute's technical field ids into an Array
    var sizes = new Array();
    var z = 0;
    for ( var c = 0; results != null && c < results.length; c++ )