adding new chunk will make $_contents and $_chunks out of sync

[jozefbriss]

php-png/src/PNG/Image.php

Line 75 in 59a7549

Adding the following or similar on line 75 of Image.php could fix the problem:

    $data_size = strlen($data);
    $chunk = array(
      'size' => $data_size + self::CHUNK_OVERHEAD_BYTES,
      'type' => $type,
      'data_size' => $data_size,
      'data' => $data,
      'raw_data' => $data,
      'crc' => crc32($type . $data),
    );
    $c = count($this->_chunks);
    $this->_chunks[$c] = $this->_chunks[$c - 1];
    $this->_chunks[$c - 1] = $chunk;