fix pro train bug causing it not to optimize when there is no held-out test set
fix pro train bug causing it not to optimize when there is no held-out test set

kho/mr-cdec,kho/mr-cdec,kho/mr-cdec,kho/mr-cdec,pks/cdec-dtrain-legacy,pks/cdec-dtrain-legacy,kho/mr-cdec,pks/cdec-dtrain-legacy,pks/cdec-dtrain-legacy,pks/cdec-dtrain-legacy,pks/cdec-dtrain-legacy,kho/mr-cdec