use then instead of catch for promise returned from a callback

lib/sequelize.js

@@ -1145,7 +1145,7 @@ module.exports = (function() {
             return transaction.commit().then(function () {
               resolve(result);
             });
-          }).catch(function (err) {
+          }).then(null, function (err) {
             transaction.rollback().then(function () {
               reject(err);
             }, function () {