### What?
Got an error in the admin panel when opening a document with richtext
and block. The error is:
`TypeError: collapsedArray.includes is not a function`
Screenshot of the error:
After reseting the preferences the error is gone. I did not take a copy
of the database before using reset settings, so I'm not sure what the
preferences where set to. So not sure how it got that way.
### Why?
Make the reading of preferences more robust against wrong data type to
avoid error.
### How?
Make sure collapsedArray is actually an array before using it as such.
b85727367c