Wordpress admin WP_table_list show incorrectly

Question

As the image above, my custom wp_list_table didn't show correctly. Code as below

<?php
if ( !class_exists( 'V2OMLVG_Video_Table' ) )
{
    class V2OMLVG_Video_Table extends WP_List_Table
    {
        function __construct ()
        {
            parent :: __construct (
                array(
                    'singular'  => 'wp_list_video',
                    'plural'    => 'wp_list_videos',
                    'ajax'      => false
                )
            );
        }

        function get_columns()
        {
            return $columns = array(
                'cb'                        => '<input type="checkbox" />',
                'col_id'                    => __('ID'),
                'col_video_title'           => __('Video Title'),
                'col_video_description'     => __('Video Description'),
                'col_created_time'          => __('Created'),
                'col_updated_time'          => __('Updated'),
                'col_last_modified_user'    => __('Last Modified User'),
                'col_video_type'            => __('Video Platform'),
            );
        }

        function column_cb($item) {
            return sprintf(
                '<input type="checkbox" name="id[]" value="%s" />', $item['id']
            );    
        }

        function col_video_title ($item, $column_name)
        {

            var_dump($item);
            $actions = array(
                'edit'      => sprintf('<a href="?page=%s&id=%s">Edit</a>', 'v2omlvg_edit_video', $item['ID']),
                'delete'    => sprintf('<a href="?page=%s&action=%s&book=%s">Delete</a>', 'v2omlvg_edit_video', 'delete', $item['ID']),
            );

            return sprintf('%1$s %2$s', $item['video_title'], $this->row_actions($actions) );
        }

        function get_bulk_actions() {
            $actions = array(
                'delete'    => 'Delete'
            );
            return $actions;
        }

        public function get_sortable_columns ()
        {
            return $sortable = array(
                'col_video_title'           => array('video_title', false),
                'col_created_time'          => array('created_time', false),
                'col_updated_time'          => array('updated_time', false),
                'col_video_type'            => array('video_type', false)
            );
        }

        function prepare_items ()
        {
            global $wpdb, $_wp_column_headers;
            $screen = get_current_screen();

            $table_name = $wpdb -> prefix . 'v2omlvg_video_gallery';

            /* -- Preparing your query -- */
            $query = "SELECT * FROM {$table_name}";

            $where = !empty( $_GET['v_type'] ) ? " WHERE video_type='" . mysql_real_escape_string( $_GET["v_type"] ) . "'" : "";
            $query .= $where;
            /* -- Ordering parameters -- */
            //Parameters that are going to be used to order the result
            $orderby    = !empty( $_GET["orderby"] ) ? mysql_real_escape_string( $_GET["orderby"] ) : 'updated_time';
            $order      = !empty( $_GET["order"] ) ? mysql_real_escape_string( $_GET["order"] ) : 'ASC';
            if ( !empty( $orderby ) & !empty( $order ) )
                $query .= ' ORDER BY ' . $orderby. ' ' . $order;

            /* -- Pagination parameters -- */
            //Number of elements in your table?
            $totalitems = $wpdb -> query ( $query ); //return the total number of affected rows
            //How many to display per page?
            $perpage = 20;
            //Which page is this?
            $paged = !empty( $_GET["paged"] ) ? mysql_real_escape_string( $_GET["paged"] ) : '';
            //Page Number
            if( empty($paged) || !is_numeric($paged) || $paged<=0 ){ $paged=1; }
            //How many pages do we have in total?
            $totalpages = ceil($totalitems/$perpage);
            //adjust the query to take pagination into account
            if( !empty($paged) && !empty($perpage) ){
                $offset = ($paged - 1) * $perpage;
                $query.=' LIMIT ' . (int) $offset . ',' . (int) $perpage;
            }

            /* -- Register the pagination -- */
            $this->set_pagination_args( array(
                "total_items" => $totalitems,
                "total_pages" => $totalpages,
                "per_page" => $perpage,
            ) );
            //The pagination links are automatically built according to those parameters

            /* -- Register the Columns -- */
            $columns = $this->get_columns();
            $hidden = array();
            $sortable = $this->get_sortable_columns();
            $this->_column_headers = array($columns, $hidden, $sortable);

            /* -- Fetch the items -- */
            $this->items = $wpdb->get_results($query);
            // echo $query;
        }

        function display_rows() {

            //Get the records registered in the prepare_items method
            $records = $this->items;

            //Get the columns registered in the get_columns and get_sortable_columns methods
            list( $columns, $hidden ) = $this->get_column_info();

            //Loop for each record
            if(!empty($records)){
                foreach($records as $rec){

                    //Open the line
                    echo '<tr id="record_'.$rec->id.'">';
                    foreach ( $columns as $column_name => $column_display_name ) {
                        //Style attributes for each col
                        $class = "class='$column_name column-$column_name'";
                        $style = "";
                        if ( in_array( $column_name, $hidden ) ) $style = ' style="display:none;"';
                        $attributes = $class . $style;


                        $wp_userdata = get_userdata( $rec->user_id );

                        $video_desc = $rec->video_description;

                        if( strlen ( $video_desc ) >= 50 )
                             $video_desc = substr($video_desc, 0, 50) . '...';

                        //Display the cell
                        switch ( $column_name ) {
                            case 'col_id':  echo '<td '.$attributes.'>'.stripslashes($rec->id).'</td>';   break;
                            case 'col_video_title': echo '<td '.$attributes.'>'.stripslashes($rec->video_title).'</td>'; break;
                            case 'col_video_description': echo '<td '.$attributes.'>'.stripslashes($video_desc).'</td>'; break;
                            case 'col_created_time': echo '<td '.$attributes.'>'.$rec->created_time.'</td>'; break;
                            case 'col_updated_time': echo '<td '.$attributes.'>'.$rec->updated_time.'</td>'; break;
                            case 'col_last_modified_user': echo '<td '.$attributes.'>'.$wp_userdata->user_login.'</td>'; break;
                            case 'col_video_type': echo '<td '.$attributes.'>'.$rec->video_type.'</td>'; break;
                        }
                    }

                    //Close the line
                    echo'</tr>';
                }
            }
        }
    }
}
?>