When any custom playlist cover is removed, the playlist is left with no image at all (see attached) instead of the default 4-album cover.
I posted this in the ongoing issues board and was told to post it as a new idea instead.
Updated on 2019-01-08
Your idea was submitted a while ago and unfortunately didn't receive the amount of kudos needed to stay active in the ideas board (100 Kudos per year).
In order to keep the Ideas Exchange clearer I'll close this idea for now, but this doesn't mean Spotify rejected this idea.
If you think this is an idea which needs to be implemented, you're welcome to post it in slightly different again :)
Have a nice day!