Hello,

I run into a problem and I have no idea hat the cause can be. Can anyone point me in the right direction?
Any help is very much appreciated!

This is the error I get:

Call to a member function FormAction() on a non-objectin /home/sites/development/000_SILVERSTRIPE/www/3_1_8/framework/forms/FormField.php on line 157, referer: http://www.bestmeat4u.hst3.nl/admin/bm-settings/

This is the code:

First SettingsAdmin.php

class SettingsAdmin extends LeftAndMain {

    private static $model_importers = array();
    static $url_segment = 'bm-settings';    
    static $menu_title = 'BM Instellingen';  
    static $menu_icon = 'bm-settings/images/icons/flexslider_icon.png';

    function getEditForm() {
        $fields = new FieldList(
            new TabSet(
                $name = "Root",
                new Tab(
                    $title='Verkoop',
                    new TabSet(
                        $name='Verkoop',
                        new Tab(
                            $title='Verkoopitems'
                        )
                    )
                )
            )
        );
        $conf=GridFieldConfig_RecordEditor::create(10);
        $emaildefault = DataObject::get('EmailDefault', '', 'SortOrder ASC');
        $grid= new GridField('EmailContent', 'EmailContent', $emaildefault, $conf);
        $fields->addFieldToTab('Root.Verkoop.Verkoop.Verkoopitems', $grid);

        return $fields;
    }
}

And EmailDeafult.php:

<?php
class EmailDefault extends DataObject {
    private static $db = array(
        'Name' => 'Varchar',
        'Description' => 'Varchar',
        'SortOrder'   => 'Int'
    );

    public function getCMSFields() {
        $fields = parent::getCMSFields();
        return $fields;
    }
}

It goes wrong in this line:
$fields->addFieldToTab('Root.Verkoop.Verkoop.Verkoopitems', $grid);

When I replace this line with this I don't get thet error and the headerfield is added to the tab.
$fields->addFieldToTab('Root.Verkoop.Verkoop.Verkoopitems', new HeaderField('Article categories', 2));

So my conclusion, it goes wrong at the moment the grid is added to the tab but why? Creating the grid doesn't give an error.