Error in FixedHeader - this.s.dt is null

summer

Hi,

I hope someone can help me with this. I have this error "this.s.dt is null" at Line 19 of FixedColumns.min.js file.
Is there something that i have missed out?
This is how i write the codes and init() is a function to initialise all binding events for the page:

var dataTableID = "#Tbl";
$(document).ready(function() {
init();
oTable = $(dataTableID).dataTable({
"sScrollX": "100%",
"sScrollXInner": "150%",
"bScrollCollapse": true
});

new FixedColumns(oTable);

});