Finally I fixed it by myself. This blank square was user with my user ID.
Solution:
I debugged the page, found the method that was actually deleting the user from a list.
Method located in the script: sites.dev.pages.extension-version-access-34fe69881859a50ed3ce.js at the line 3654.
I put breakpoint here, replaced value in variable e.userID with my username and this blank square disappeared. Simple as that.
I’m just curious what’s taking so long for the Twitch team to fix this simple bug?