protected function readNext($handle, $chunkSize)
    {
        if (feof($handle)) {
            return null;
        }

        $row = $this->readRow($handle, $chunkSize);

        if (!$this->startAtRow && $this->hasHeader && !$this->headerRowSkipped) {
            $this->headerRowSkipped = true;
            return $this->readNext($handle, $chunkSize);
        }

        return $row === [] ? $this->readNext($handle, $chunkSize) : $row;
    }