Spec.Operand.Image field has gone through a couple of changes:
1. In 4.12 it was made mandatory. User had to set it in the NFD CR, or it could be set by OLM, in case NFD CR was installed via OLM. This could cause problems during operator upgrade, since the CR is not upgraded, and the user needed to changed the field explicitly
2. In 4.19 it was made optional: in production, user does not need to set it at all.The field is set by the operator, and this solves the upgrade issue.
When upgrading to 4.19 version from an earlier version, the CR must be updated: the Spec.Operand.Image value must be removed from the CR