If markDefs is null, .find breaks

Not sure what happened here, but we have a Sanity instance. Apparently occasionally after duplicating or copying a content block, like our 'rich text' (which is just the WYSIWYG editor), the 'markDefs' may be null.

I genuinely don't know why this happens, but when it does, I get this error:

TypeError: Cannot read properties of null (reading 'find')
    at buildMarksTree (file:///Users/.../web/node_modules/@portabletext/toolkit/dist/index.js:89:34)
    at serializeBlock (file:///Users/.../web/node_modules/@portabletext/react/dist/index.js:381:16)
    at renderBlock (file:///Users/.../web/node_modules/@portabletext/react/dist/index.js:319:29)
    at renderNode (file:///Users/.../web/node_modules/@portabletext/react/dist/index.js:225:323)
    at <unknown> (file:///Users/.../web/node_modules/@portabletext/react/dist/index.js:207:44)
    at Array.map (<anonymous>)
    at PortableText (file:///Users/.../web/node_modules/@portabletext/react/dist/index.js:207:23)
    at renderWithHooks (file:///Users/.../web/node_modules/react-dom/cjs/react-dom-server.browser.development.js:5658:16)
    at renderIndeterminateComponent (file:///Users/.../web/node_modules/react-dom/cjs/react-dom-server.browser.development.js:5732:15)
    at renderElement (file:///Users/.../web/node_modules/react-dom/cjs/react-dom-server.browser.development.js:5957:7)
    at renderNodeDestructiveImpl (file:///Users/.../web/node_modules/react-dom/cjs/react-dom-server.browser.development.js:6115:11)
    at renderNodeDestructive (file:///Users/.../web/node_modules/react-dom/cjs/react-dom-server.browser.development.js:6087:14)
    at renderNode (file:///Users/.../web/node_modules/react-dom/cjs/react-dom-server.browser.development.js:6270:12)
    at renderHostElement (file:///Users/.../web/node_modules/react-dom/cjs/react-dom-server.browser.development.js:5642:3)
    at renderElement (file:///Users/.../web/node_modules/react-dom/cjs/react-dom-server.browser.development.js:5963:5)

So, for some reason:

I'm able to see where this is happening: https://github.com/portabletext/toolkit/blob/acf4977c232bcc9ec6c9132a2783d87e6fdf2f1a/src/buildMarksTree.ts#L93

Not sure this is widespread or not, but in code, I've got this helper now:

  function sanitizeData(data) {
    return data.map((block) => ({
      ...block,
      markDefs: block.markDefs || []
    }));
  }

Either way, it seems that having that fall back or doing a check on markDefs may be the right call? Or this is an edge error in our editor.

Start at src/buildMarksTree.ts around line 93, where the reported .find failure occurs, and trace how a block with markDefs set to null reaches it. Reproduce the Portable Text rendering case from the report and confirm the chosen handling no longer throws while preserving normal markDefs behavior.