fixed cct plugin to not die if there is no cct instruction in a descriptor
fixed cct plugin to not die if there is no cct instruction in a descriptor

this enables to have cct plugin enabled even for descriptor without cct sections
this is usefull for converting images to cct - we have same dogen command for cct and cct descriptors

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