getFileUploadError example

$files = $event->getData();

                if (!\is_array($files)) {
                    $files = [];
                }

                foreach ($files as $file) {
                    if ($requestHandler->isFileUpload($file)) {
                        $data[] = $file;

                        if (method_exists($requestHandler, 'getUploadFileError') && null !== $errorCode = $requestHandler->getUploadFileError($file)) {
                            $form->addError($this->getFileUploadError($errorCode));
                        }
                    }
                }

                // Since the array is never considered empty in the view data format                 // on submission, we need to evaluate the configured empty data here                 if ([] === $data) {
                    $emptyData = $form->getConfig()->getEmptyData();
                    $data = $emptyData instanceof \Closure ? $emptyData($form, $data) : $emptyData;
                }