TypeError when switching to a parent element while highlighting a child element

Sentry Issue: ARKINDEX-FRONTEND-AGY

1. Open a page that has text lines. If you browsed around the frontend to find it, press F5 once you opened the page.
2. Select a text line in the children tree.
3. Open the dev tools.
4. Click on a parent folder in the header.
5. Watch the console fill up with red error messages.
6. Cry.