title: Second row header for fixed column in datatable
body: <p>I need to implement 3 rows header with fixed columns. So I appended the header rows to header on dataSrc callback. Below is how I added rows to header.</p>
  
  <pre><code>       function createHeaders(headeData){
  
         //.... creating firstHeaderRow
         //.... creating secondHeaderRow
              $('thead tr:first-child').before(firstHeaderRow);
              $('thead tr:last-child').after(secondHeaderRow);
         }
  </code></pre>
  
  <p>My table configured like below:</p>
  
  <pre><code>       $('#tableElement').DataTable({
             fixedColumns : {
                 leftColumn: 5,
                 rightColumn: 2
             },
             ajax:  {
                 dataSrc: function(data){
                      createHeaders(data.headerData);
                  }
             }
         });
  </code></pre>
  
  <p>The problem is in this case firstHeaderRow and secondHeaderRow is  not showing for fixedColumns. (It's showing for non-fixed columns correctly)</p>
  
  <p>Based on documentation I think I need to call fnRedrawLayout()</p>
  
  <p>So I added below lines at the bottom of createHeaders function</p>
  
  <pre><code>        var table = $('#tableElement').dataTable();
          var fc = new $.fn.dataTable.FixedColumns( table,  {
               leftColumn: 5,
               rightColumn: 2
          });
          fc.fnRedrawLayout();
  </code></pre>
  
  <p>However I am getting this error on FixedColumn.min</p>
  
  <pre><code>       Uncaught TypeError: Cannot read property 'style' of null on below line.
  
         a.wrapper.style.height=e+"px";0&lt;this.s.iLeftColumns&amp;&amp;(a.left.wrapper.style.width=g+"px",a.left.wrapper.style.height="1px",a.left.body.style.height=
  </code></pre>
  
  <p>Any help is much appreciated to get this working.</p>