MarkDefs sometimes missing in block content

[heggemsnes]

Describe the bug

I haven't been directly able to reproduce it, but our editors sometimes are able to create block content like this:

Excerpt from entire content:

"content": [
    {
      "_key": "8443f579db40",
      "_type": "block",
      "children": [
        {
          "_key": "455a4ebd387e",
          "_type": "span",
          "text": "For at et tiltak skal virke som tenkt, så må man følge opp og være tro mot den anbefalte måten å jobbe på. Å etterleve anbefalt arbeidsmåte er altså en forutsetning for å oppnå best mulig effekt av tiltak."
        }
      ],
      "style": "normal"
    },
    {
      "_key": "b6b2382edd59",
      "_type": "block",
      "children": [
        {
          "_key": "04c4e6416c7b",
          "_type": "span",
          "text": "Fagfolk kaller dette for «implementeringskvalitet», noe som det slett ikke er lett å få til å vare over lang tid i skolen."
        }
      ],
      "style": "normal"
    },
  ],

Where the markDefs are not set. This causes issues in the portableText render as the @portabletext/react expects there to be an array where it is now undefined or null.

To Reproduce

This is the problem, I can't reproduce it... Will check more with the editing flow of our editors.

Expected behavior

Empty array of markDefs should be set.

Which versions of Sanity are you using?
3.63.0

What operating system are you using?

MacOS

Which versions of Node.js / npm are you running?

10.2.4
v20.11.0

Additional context

I'm currently handling it in my frontend by just adding an empty array.