TYPO3 Core

When I'm in a translated record (here: a powermail-form) and click on "Localize all records" to translate inline-records (here: pages and fields of the form) I get a Error 500 from the server, in return to an AJAX-call.

The raw result shows:
Exception
#1: PHP Warning: Invalid argument supplied for foreach() in /var/www/typo3_src-git/typo3/sysext/backend/Classes/Form/FormEngine.php line 1274

Which is in the context of required fields, it seems:
01272: $out = '';
01273: // Required:
01274: foreach ($this->requiredFields as $itemImgName => $itemName) {
01275: $match = array();
01276: if (preg_match('/^(.+)\\[((\\w|\\d|_)+)\\]$/', $itemName, $match)) {