I don't think this is fixed yet. There are two problems…
PROBLEM #1
The exising deleted groups that already appeared in the list are still showing up. Maybe you can tell me what to look for in the DB and I can remove them that way?
PROBLEM #2
Go to User-> Groupd and create 3 new groups (say Group A, Group B and Group C) but do NOT assign them to anybody when you first create them.
Also create 2 new pages, say MyPage and MySubPage. Put MySubPage underneath MyPage, so that MyPage is the parent.
Now go to Roles-> Pages and choose "Assign for selected and sub-pages", then tick Group A and Group B and Group C. Scroll down to MyPage and tick Page Editor, and add all three groups to this page (click Update). Now scroll back down and confirm that all three groups show up as Page Editors in MyPage and as {Page Editors} in MySubPage.
Now go to Users-> Groups and delete the middle group (alphabetically), which in my example is Group B. Delete only the ONE group.
Now go back to ROles-> Pages and scroll down to MyPage and you will see an empty set of commas:
Groups: Group A, , GroupC
Now check MySubPage and will see an empty set of curly brackets:
Groups: {Group A}, {}, {Group C}