Error in sortable.esm.js

[Siderite]

Exact URL of where the bug happened

https://lichess.org/study/wvNVfl58/9gMbkk8O

Steps to reproduce the bug

I don't know how to reproduce it consistently. This happened in the study chapters list on mouseover. After refresh I couldn't reproduce it anymore except accidentally. I believe it is connected to the server analysis tab, maybe related to navigating via the blunder summary, but I couldn't reproduce it consistently.

What did you expect to happen?

No error.

What happened instead?

Error, see additional info.

Operating system

Windows 11

Browser and version (or alternate access method)

Brave

Additional information

{
"TypeError": "Cannot read properties of null (reading 'options')",
"stack": "TypeError: Cannot read properties of null (reading 'options')\n at https://lichess1.org/assets/npm/sortable.esm.js:976:41\n at Array.some ()\n at _detectNearestEmptySortable (https://lichess1.org/assets/npm/sortable.esm.js:975:15)\n at HTMLDocument.nearestEmptyInsertDetectEvent (https://lichess1.org/assets/npm/sortable.esm.js:1046:19)"
}

sortable is <div class="study__chapters">...</div>
expando is Sortable1737718027267
sortable.Sortable1737718027267 is null