isUint8ListEqual bug

[devinzhang91]

https://github.com/bcgit/pc-dart/blob/59e06028bff338adc7d25ff9da4063a3b2e28b4c/tutorials/examples/rsa-demo.dart#L294

if (a.length == b.length) {
  ...
} else {
  return false;
}
return true;