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

[Martin Schnitkemper]

Hello,

I tried to extend okular to save PDF-Print-Options (wish #463732).  All works 
well so far, I added a new item in the configuration dialog and the new 
variable "PageScaleMode" is written to and read from "okularpartrc", but I am 
not able to assign the value of "Okular::Settings::pageScaleMode" to 
"m_scaleMode->setCurrentIndex" in module "generator_pdf.cpp".

Compilation is successful, but it crashes on runtime after opening the print 
dialog. Message on terminal is "you need to call Settings::instance before 
using".

I am not too familiar with C++ coding and it is my first try to extend an 
application.  I inspected already the other modules of the project where the 
developers used "Okular::Settings::" in a similar & working way, but I could 
not find out so far, where the instance has been set for a proper usage.

Can anyone tell me what I missed, or guide me to a code example of the okular 
project where I can see how to get right access to the "Okular::Settings::"? 

Thank you in advance for your support,
Martin