OpenPGP: Read some empty DOs from Gnuk.
OpenPGP: Read some empty DOs from Gnuk.

In Gnuk, some empty DOs are returned as not exist, instead of existing with empty value.
So, we will consider them exist in driver.

hhonkanen/OpenSC,kasparsd/opensc-latvia-id,tidatida/OpenSC,dengert/OpenSC,aobaid/OpenSC,frankmorgner/OpenSC,gemini/OpenSC,viktorTarasov/OpenSC-SM,aobaid/OpenSC,philipWendland/OpenSC,martinpaljak/OpenSC,hongquan/OpenSC-main,rickyepoderi/OpenSC,martinpaljak/OpenSC,viktorTarasov/OpenSC-SM,gemini/OpenSC,fabled/OpenSC,frankmorgner/OpenSC,kasparsd/opensc-latvia-id,mtrojnar/OpenSC,LudovicRousseau/OpenSC,philipWendland/OpenSC,jpki/OpenSC,germanblanco/OpenSC,mtrojnar/OpenSC,viktorTarasov/OpenSC-SM,mouse07410/OpenSC,Jakuje/OpenSC,dengert/OpenSC,jpki/OpenSC,dengert/OpenSC,velter/OpenSC,nmav/OpenSC,l1k/OpenSC,OpenSC/OpenSC,LudovicRousseau/OpenSC,CardContact/OpenSC,Jakuje/OpenSC,metsma/OpenSC,mtrojnar/OpenSC,gemini/OpenSC,metsma/OpenSC,mouse07410/OpenSC,velter/OpenSC,AktivCo/OpenSC,mouse07410/OpenSC,velter/OpenSC,frankmorgner/OpenSC,l1k/OpenSC,metsma/OpenSC,aobaid/OpenSC,kasparsd/opensc-latvia-id,germanblanco/OpenSC,OpenSC/OpenSC,nmav/OpenSC,frankmorgner/OpenSC,LudovicRousseau/OpenSC,tidatida/OpenSC,UIKit0/OpenSC,tidatida/OpenSC,UIKit0/OpenSC,AktivCo/OpenSC,fabled/OpenSC,hhonkanen/OpenSC,rickyepoderi/OpenSC,UIKit0/OpenSC,tidatida/OpenSC,AktivCo/OpenSC,aobaid/OpenSC,jpki/OpenSC,hongquan/OpenSC-main,OpenSC/OpenSC,fabled/OpenSC,philipWendland/OpenSC,kasparsd/opensc-latvia-id,fabled/OpenSC,l1k/OpenSC,martinpaljak/OpenSC,CardContact/OpenSC,nmav/OpenSC,velter/OpenSC,germanblanco/OpenSC,UIKit0/OpenSC,Jakuje/OpenSC,hongquan/OpenSC-main,rickyepoderi/OpenSC,hhonkanen/OpenSC,CardContact/OpenSC,Jakuje/OpenSC