Spurious Error Message When Saving User With Non-Admin Rights

[memiamp]

Describe the problem/bug
When modifying non-admin users on the Server Settings, if the Is Admin checkbox is left unchecked and the Save button is pushed, a spurious error is shown that states:

This is the only Admin, so their role can't be removed until another Admin is added.

The account being modified was not actually an admin (so the Is admin checkbox was unchecked), and is not the current admin account I am logged in with.

Your environment

• Version of BTCPay Server: 1.0.5.2
• Deployment method: Docker on Ubuntu
• Other relevant environment details: N/A

Logs (if applicable)
N/A

Setup Parameters
N/A

To Reproduce
Steps to reproduce the behavior:

1. Go to Server Settings -> Users.
2. Create a new user account.
3. Edit the new user account.
4. Leaving Is admin unchecked, click Save.
5. Receive the error message as shown in the screenshot.

Expected behavior
The error message should not be displayed. The user account was not an admin to begin with, and the account being edited is not the admin account I am logged in with.

Actual behavior
As described above.

Screenshots/Links

Additional context
N/A