Changing AuthName and Password of a user account throws error

[fexs]

When trying to change the AuthName of a sip account and the associated password an error is thrown in the web interface as following:

We're sorry, but something went wrong.

Please take a minute and report an issue at https://github.com/amooma/GS5/issues or contact your admin.

Further testing revealed that a change of the AuthName as a single step is possible. However, trying to change the password in a separate step still fails. So the problem seems to be with changing the password of the sip account.