'leave' 'group' event is not triggered correctly in subgroups

[oseg]

Scenario:
1- login as "user1"
2- Create an open group called "Parent group"
3- Create an open subgroup of "Parent group" called "Child group"
4- Create an open subgroup of "Child group" called "Grandchild group"
5- Create another open subgroup of "Child group" called "Another grandchild group"
6- login as "user2"
7- Join "Parent group", "Child group" and "Grandchild group" groups, but NOT "Another grandchild group"
8- Leave "Parent group"

Results:
Let's focus on groups_user_leave_event_listener() which is registered on 'leave' 'group' event for instance, but we could have focus on any event handler registered on 'leave' 'group' event.

groups_user_leave_event_listener() is called once for "Parent group" and "Child group", but it is called twice for "Grandchild group" and "Another grandchild group"

Expected results:
groups_user_leave_event_listener() should be called once for "Parent group", "Child group" and "Grandchild group" and should not be called for "Another grandchild group"