Trying to send a legacy form with an empty File Upload field. I get:
Whoops \ Exception \ ErrorException (E_WARNING)
Undefined array key 6
/updates/concrete-cms-9.1.3/concrete/blocks/form/controller.php
} elseif ($row['inputType'] == 'fileupload') {
$answerLong = '';
$answer = (int) ($tmpFileIds[(int) ($row['msqID'])]); <-- Error line 479
if ($answer > 0) {
$answerDisplay = File::getByID($answer)->getVersion()->getDownloadURL();
} else {
$answerDisplay = t('No file specified');
}