Runtime error "you need to call Settings::instance before using"

[Martin Schnitkemper]

Am Samstag, 25. Februar 2023, 11:41:42 CET schrieb Albert Astals Cid:

> Why are you adding PDF only options to the general config file and general
> config dialog instead of to the PDF generator config file and PDF generator
> config dialog/page?

Moved the configuration to the Backend Configuration, looks now like this:
https://invent.kde.org/martin-de/okular/uploads/82757d49a7fe7daa4ffa872f5f6ca4b6/Screenshot_20230225_144426.png

It seems to work now: the configuration is saved and can be retrieved and set
as default before printing, and the print dialog no longer crashes after
invoking it.

Should I create a merge request now?

Cheers,
Martin