Leave (or be removed from) a parent group should display an error if user owns a subgroup

[oseg]

Scenario1:
1- Login as user1
2- Create an open group called "Parent group"
3- Enable "Enable Sub-Groups for this group"
4- Login as user2
5- Join "Parent Group"
6- Create an open subgroup called "Child group"
7- Go to "Parent group" profile page and click on "Leave group" button
-> The message "Successfully left group" is displayed
=> User2 successfully left "Parent Group" and "Child group", but user2 still owns "Child group".
This situation should not happen.

Expected results:
An error message saying that the user can not leave the parent group because he owns a subgroup

Scenario2: same as scenario1, but replace step7 by:
7- Login as user1, go to the "Parent group" profile page, click on "user2" icon in group members list
8- In the popup menu, click on "Remove from group"
-> The message "Successfully removed user2 from group" is displayed
=> User2 has been successfully removed from "Parent Group" and "Child group", but user2 still owns "Child group".
This situation should not happen.

Expected results:
An error message saying that the user can not be removed from parent group because he owns a subgroup