finish method Null safety

List<int>? finish()

Implementation

List<int>? finish() {
  List<int>? bytes;

  if (output == null) {
    return bytes;
  }

  _writeChunk(output!, 'IEND', []);

  sequenceNumber = 0;

  bytes = output!.getBytes();
  output = null;
  return bytes;
}