The page at http://localhost says:ERROR [Notice]: Undefined index:
IN POST /test/silverstripe/admin/newsletter/EditForm?fieldName=Recipients&action_callfieldmethod&methodName=addtogroup
Line 101 in /Sites/test/silverstripe/cms/code/MemberTableField.php

Source
======
92:          $csvFieldList[$field] = $field;
93:       }
94:       
95:       if($group) {
96:          if(is_object($group)) {
97:             $this->group = $group;
98:          } elseif(is_numeric($group)) {
99:             $this->group = DataObject::get_by_id('Group', $group);
100:          }
* 101:       } else if(isset($_REQUEST['ctf']) && is_numeric($_REQUEST['ctf'][$this->Name()]["ID"])) {
102:          $this->group = DataObject::get_by_id('Group', $_REQUEST['ctf'][$this->Name()]["ID"]);
103:       }
104:
105:       foreach(self::$addedFields as $key => $value) {
106:          $fieldList[$key] = $value;
107:       }

<ul>MemberTableField->__construct(NewsletterAdmin,Recipients,)
line 339 of NewsletterAdmin.php

NewsletterAdmin->getMailingListEditForm(1)
line 273 of NewsletterAdmin.php

NewsletterAdmin->MailingListEditForm()
line 247 of NewsletterAdmin.php

NewsletterAdmin->EditForm(HTTPRequest)
line 167 of Controller.php

Controller->handleAction(HTTPRequest)
line 131 of RequestHandler.php

RequestHandler->handleRequest(HTTPRequest)
line 127 of Controller.php

Controller->handleRequest(HTTPRequest)
line 282 of Director.php

Director::handleRequest(HTTPRequest,Session)
line 123 of Director.php

Director::direct(/admin/newsletter/EditForm)
line 122 of main.php