[BUG] Don't allow first admin to revoque its own admin rights

[watchoutfreedom]

🐞 Describe the Bug

A clear and concise description of what the bug is.

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🔍 Steps to Reproduce

Steps to reproduce the behavior:

1. after creating a network, With the admin account, Go to profile
2. Click on ...
3. Click on revoque admin rights
4. No one can admin the network any more.

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🤔 Expected Behavior

Block revoque administrator if there's just one admin, or if this admin is the first

[albjeremias]

17601e8 don't allow user to change it's own role