Is it possible that blobUploadError isn't present but blobHash or encryptionKey is null?

As explained in D8589 I wanted to avoid indentation.

It is impossible.

1. Typing of blobServiceUpload returns either non-null blobUploadError or the pair of non-null blobHash and encryptionKey.
2. encryptionKey is generated by awaiting this function:

async function generateKeyCommon(commonCrypto: Crypto): Promise<Uint8Array> {
  const algorithm = { name: 'AES-GCM', length: 256 };
  const key = await commonCrypto.subtle.generateKey(algorithm, true, [
    'encrypt',
    'decrypt',
  ]);
  const keyData = await commonCrypto.subtle.exportKey('raw', key);
  return new Uint8Array(keyData);
}

it cannot return null.

3. blobHash is calculated by this function: https://nodejs.org/api/crypto.html#cryptocreatehashalgorithm-options. It cannot return null.