TYPO3 Core

Assume the following TCA:

        'mail_files' => array(
                'exclude' => 1,
                'label' => 'LLL:EXT:webconinstance/Resources/Private/Localization/locallang_db.xml:tx_seminars_seminars.mail_files',
                'config' => array(
                        'type' => 'group',
                        'internal_type' => 'file',
                        'allowed' => 'pdf,xls,xlsx',
                        'uploadfolder' => 'uploads/tx_seminars/',
                        'size' => 10,
                        'MM' => 'tx_seminars_seminars_mail_files_mm',
                        'maxitems' => 10,
                        'wizards' => $tempWizardSend,
                ),
        ),

When trying to save any files to such a field this will cause an error when trying to update refindex
See attached screenshot

The problem seems to be caused by the following lines because $this->currentTable isn't set.

                        // Update ref index; In tcemain it is not certain that this will happen because
                        // if only the MM field is changed the record itself is not updated and so the ref-index is not either.
                        // This could also have been fixed in updateDB in tcemain, however I decided to do it here ...
                        $this->updateRefIndex($this->currentTable, $uid);