Produce empty output item in ozn file if no output is present in model
Produce empty output item in ozn file if no output is present in model

nathanielbaxter/libminizinc,tias/libminizinc,jjdekker/libminizinc,jjdekker/libminizinc,jjdekker/libminizinc,nathanielbaxter/libminizinc,nathanielbaxter/libminizinc,tias/libminizinc,nathanielbaxter/libminizinc,jjdekker/libminizinc