Fun groups bug

[CrazyHackGUT]

What are the steps to reproduce this issue?

1. Open "Groups" in web-panel.
2. Create 2 groups with names "Administrator" and "Creator"
3. Rename "Creator" to "Administrator"

What happens?

We have two same groups by name, but different by access and inherited users.

What were you expecting to happen?

SourceBans should display error like Group "Administrator" already exists when i try edit name.

Any other comments?

See this video for more information: https://youtu.be/B44ynXBBM9Q

What versions of software are you using?

Operating System: Ubuntu 16.04 LTS
SourceBans++ Version: 1.5.4.7 (this bug also exists in last 1.6.3 version)
PHP Version: 7.1.11
MySQL Version: 5.7.21
Link to your project: https://bans.g-44.ru/ (I'm not sure that it's necessary at all)
Link to a phpinfo() output: https://bans.g-44.ru/phpinfo.php (I'm not sure that it's necessary at all)

[CrazyHackGUT]

If we rename server admin group, all admins from 2 groups merges to 1.
If we rename web admin group, all ok.