refactor: remove validation from converter

[DennisGarding]

Remove all checks, which results in an empty Convert Result. These should be catches by the later entity validation

[MalteJanz]

Please add a short PR description 🙂 . E.g. questions I would like to see answered in it:

• What type of checks are being removed, e.g. checks for entity fields that are required in SW6 and would produce another log entry otherwise in the later entity validation
• What other type of checks are removed and what's the reasoning behind it. E.g. does the user still get notified about errors in optional fields? Or are they just silently set to null?