If the base image is 'scratch', do not add a version
If the base image is 'scratch', do not add a version

Fixes #55

jboss-dockerfiles/dogen,jboss-container-images/concreate,jboss-dockerfiles/dogen,jboss-dockerfiles/dogen,goldmann/dogen,jboss-container-images/concreate,goldmann/dogen,jboss-container-images/concreate,goldmann/dogen