Fix: Optional field throws exception in case of null value in ilSoapTestAdministration

[sKarki999]

This PR address the issue: https://mantis.ilias.de/view.php?id=47008
The solution has already been discussed in the PR for release 9: #10510
I have provided this PR for release 10.
PR for release 11 and trunk will follow.

[kergomard]

Hi @sKarki999

A quick reaction as this interacts with the functioning of the Test: This doesn't look right. Why are values being written to the XML, when they do not exist? You are setting missing question-titles, question-ids and so on. This to me looks like you are trying to write results where there aren't any. Probably just skipping the statements when the values are missing would be the right move? I did not look up or down the execution chain, but this looks like somebody might then have the splendid idea of writing this back into ILIAS through SOAP again, where things are written directly to the database tables of the test and then things start going sideways in ways that we will not be able to figure out, even if we debug until kingdom come. Might there be a way to treat the root cause instead of suppressing symptoms?

In any case I would prefer to keep the current situation instead of changing this for existing versions. As far as I can see, nobody complained, as the issue was written by your colleague, if I'm right.

I know, this is at a difficult interface between components that are not designed for interacting in this way and it wasn't you who has built it this way, without thinking about the consequences, but sadly, we now have to live with them.

Thank you very much and best,
@kergomard