Mantis #47008 Prevent writing null to xml for non required fields

[laurinoetterli]

If any not required field contains null, this throws an exception. It is fixed by writing a default value to the xml if it is null.

[dsstrassner]

Hi @laurinoetterli, please look at our documentation. If this is a bug fix, we need a Mantis issue link. Otherwise this is an improvement, and then other rules apply.
Thanks for your contribution!

[mjansenDatabay]

Hi @GitHamo ,

we leave it up to you how to proceed with this PR. As @dsstrassner mentioned above, bugfixes usually need a corresponding Mantis issue.

Best regards,
Michael

[GitHamo]

Hey everyone, I have created a Mantis ticket for the issue and added the PR to it. Please update the PR info and let me know if the ticket description is invalid.

Now, since this is only for release_9, but the issue is also in further releases, which will be supported longer than version 9, similar PRs for release_10, release_11 & trunk branches should be created.

@laurinoetterli Thank you for your contributions.

[laurinoetterli]

After some more testing i have found, that the login, firstname and lastname fields also might be null if the user was deleted.