Destroy table troubles

I'm not sure why I'm having so much trouble with this.. I'm trying to destroy a table. The error is: Uncaught TypeError: Cannot read property 'dt' of undefined

Code:

I have a function that's triggered by a dropdown select menu.

var table

function onChange() {

if ( table != null ) {
    table.destroy();
    $("#weeklySalesTable").empty();
}

...

table = $('#weeklySalesTable').DataTable( {
                          "scrollY": "600px",
                          "scrollX": true,
                          "paging": true,
                          "lengthMenu": [ [25, 50, 100], [25, 50, 100] ],
                          "info": true,
                          "deferRender": true,
                          "ordering": false,
                          "fixedColumns":   true,
                          "scrollCollapse": true,
                    } );

}