a.rows is undefined

This is a snippet of my code, this adds header information to the grid so I can use the same report view for different sections.

   $(document).ready(function(){
            mygrid = new dhtmlXGridObject('Report');
            mygrid.setImagePath("js/dhtmlxGrid/codebase/imgs/");
            mygrid.setEditable(false);
            mygrid.enableAutoHeight(true,400);

    //        mygrid.setHeader(" ");
    //	mygrid.setColTypes ("ed");
    //	mygrid.setInitWidths("1");
    //	mygrid.setColSorting("int");
    //	mygrid.setColAlign("left");
    //	mygrid.setColVAlign("middle");
            <?php 
                $item = array_shift($ctx->grid_header);
                print "mygrid.setHeader('{$item['name']}');\n";
                print "mygrid.setColTypes('{$item['type']}');\n";
                print "mygrid.setInitWidths('{$item['width']}');\n";
                print "mygrid.setColSorting('{$item['sort']}');\n";
                print "mygrid.setColAlign('{$item['align']}');\n";
                print "mygrid.setColVAlign('{$item['valign']}');\n";
            ?>
            mygrid.attachHeader("#text_filter,#select_filter,&nbsp;,&nbsp;,&nbsp;,&nbsp;,&nbsp;,&nbsp;,&nbsp;");
            mygrid.attachFooter("Totals,,,#stat_total,#stat_total,,#stat_total,,<span>$</span><span style=\"padding-right:2px;color:green;\">{#stat_total}</span>");
            
            mygrid.setSkin("dhx_alto");
            mygrid.init();
            mygrid.enableSmartRendering(true);
            
        <?php
            foreach ($ctx->grid_header as $index => $column){
                print  "mygrid.insertColumn(".($index+2).", '{$column['name']}', '{$column['type']}', {$column['width']}, '{$column['sort']}','{$column['align']}','{$column['valign']}');\n";
            }
        ?>

The code that follows inserts the data, however, I am getting a:

a.rows is undefined.

Unfortunately the issue cannot be reconstructed.
If issue still occurs - please provide a complete demo.