Fix a critical warning when loading a PKCS-7 certificate with no DN
Fix a critical warning when loading a PKCS-7 certificate with no DN

hughsie/fwupd,vathpela/fwupd,hughsie/fwupd,fwupd/fwupd,hughsie/fwupd,fwupd/fwupd,hughsie/fwupd,vathpela/fwupd,fwupd/fwupd,vathpela/fwupd,fwupd/fwupd,vathpela/fwupd