fixed empty password issue

lib/sequelize/Sequelize.js

@@ -3,7 +3,7 @@ var Sequelize = function(database, username, password, options) {
   this.config = {
     database: database,
     username: username,
-    password: (((["", null, false].indexOf(password) > -1) || (typeof password == 'undefined')) ? "" : password),
+    password: (((["", null, false].indexOf(password) > -1) || (typeof password == 'undefined')) ? null : password),
     host    : options.host || 'localhost',
     port    : options.port || 3306
   }