Product options values array contains null

[elizabethy]

We recently received a products/update webhook from Shopify that included the following data.  The weird thing to note is that the second options object's values array only contains null.  Is that intended to be valid behavior?  What does it represent, conceptually?

{
   ...
  "variants": [
    {
      ...
      "option1": "Default Title",
      "option2": null,
      "option3": null,
      ...
    }
  ],
  "options": [
    {
      ...
      "name": "Color",
      "position": 1,
      "values": [
        "Default Title"
      ]
    },
    {
      ...
      "name": "Size",
      "position": 2,
      "values": [
        null
      ]
    }
  ],
  ...
}