check if id does not exist a bit more explicitly

if left as-is, ids with value of zero were treated as non-existent

lib/dao.js

@@ -361,7 +361,7 @@ DataAccessObject.updateOrCreate = DataAccessObject.upsert = function upsert(data
   var hookState = {};
 
   var id = getIdValue(this, data);
-  if (!id) {
+  if (id === undefined || id === null) {
     return this.create(data, options, cb);
   }