When delete group, no warning dialog that permissions should be given to another group

Preconditions:
1. Branch "Test" is created;
2. Group1 granted permissions View_Topic for branch "Test"
3. User1 is a member of Group1
4. Group1 is the only group that has permissions to "Test" branch

How to reproduce:
1. Go to Admin panel
2. Delete Group1

AR: Group deleted, no warning dialog
ER: Warning dialog that permissions of deleted group should be given to another group