Ineffective Groups on the Global Permissions page are removed in some scenarios

Steps to reproduce:

1. Open Global Permissions page, fisheye-users group is shown as "FishEye user" and crucible-users is shown as "FishEye & Crucible user".
2. Remove FishEye license key, on the Global Permissions page it shows fisheye-users as "None" and crucible-users as "Crucible user".
3. Click on fisheye-users "None" drop-down and select "None" again. (Probably an update is performed under the hood, despite value is the same).
4. Restore FishEye license key.
5. Open Global Permissions page, the fisheye-users group has been deleted.

Another way to achieve a similar result without toggling licences:

1. Open Global Permissions page, change fisheye-users group to "None". Group is still visible on the list.
2. Reload Global Permission page, the fisheye-users group disappears.

It seems that whenever any group is "None" and has not "Can add repository" permission enabled, then such row is being deleted automatically (as it has no effect). However this is not reflected in the UI immediately.
Note this affects UX only, no impact on effective permissions so no security risk identified.

Possible fixes:

1. remove such row immediately (although then user would have no chance to follow the flow "change to None, enable can add repo toggle")

2. grey out the entire row indicating that it has no effect, give a hint that it will be removed

3. keep the row. user would have to click the delete icon explicitly. 

also regarding the problem with switching license keys:

4. If user selects the same value from a drop-down, then do not update the value under the hood (as the "None" may mean either "None" for FECRU or "Fisheye" for CRU instance; similarly "FishEye" may mean "FishEye" for FECRU or "FishEye and Crucible" for FE instance).