App Icon has Unassigned Image error

I had the same issue! The solution that worked for me was pretty easy:

Just select the unassigned image and delete it via delete button. Clean and Build. Done.

Hope this helps!

(That's assuming you didn't miss any of the required images)

I had this problem a while ago: I went into the media.xcassets directory and checked the contents.json file, where I found some entry with "unassigned" set to TRUE. I removed it and it removed the compiler warning.

Hope you got stuck in that same scenario so you will also be able to fix it.