@CanIgnoreReturnValue
    public Builder setSalt(Bytes salt) {
      if (salt.size() == 0) {
        this.salt = null;
        return this;
      }

      this.salt = salt;
      return this;
    }
Defaults to null if not set.
java_src/src/main/java/com/google/crypto/tink/hybrid/EciesParameters.java