don't merge nil criteria from chain results

src/scribe/filecontent.go

@@ -105,7 +105,9 @@ func (f *filecontent) fireChains(d *Document) ([]evaluationCriteria, error) {
 			if err != nil {
 				return nil, err
 			}
-			oc.mergeCriteria(criteria)
+			if criteria != nil {
+				oc.mergeCriteria(criteria)
+			}
 
 			// Extract the criteria. Rewrite the identifier based
 			// on what identifier was used for the chain.

src/scribe/object.go

@@ -83,7 +83,9 @@ func (o *object) fireChains(d *Document) error {
 		o.err = err
 		return err
 	}
-	si.mergeCriteria(criteria)
+	if criteria != nil {
+		si.mergeCriteria(criteria)
+	}
 	return nil
 }