[Klarna] [Checkout v2] Bug: if «orderid1» or «orderid2» optional field inside «merchant_reference» is empty, then an «order» request fails with the message «Bad format»

The orderid1 and orderid2 fields inside ‘merchant_reference’ are marked as optional in the documentation:

But when any of them is empty, then an «order» API request fails.

    "merchant_reference": {
        "orderid1": "1",
        "orderid2": ""

The Klarna’s server responds:

Bad format: merchant_reference`

See also:

I have got an answer from the Klarna’s support:

The orderid2 is optional.
However it is not possible to send in an empty value, if you wish to send it, please add a value.