Fixed isActual syntax to accept optional model arg

lib/mysql.js

@@ -693,7 +693,18 @@ MySQL.prototype.createTable = function (model, cb) {
  */
 MySQL.prototype.isActual = function(models, cb) {
   var self = this;
-  var ok = false;
+
+  if ((!cb) && ('function' === typeof models)) {
+    cb = models;
+    models = undefined;
+  }
+  // First argument is a model name
+  if ('string' === typeof models) {
+    models = [models];
+  }
+
+  models = models || Object.keys(this._models);
+  
   async.each(Object.keys(models), function(model, done) {
     var table = self.tableEscaped(model);
     self.query('SHOW FIELDS FROM ' + table, function(err, fields) {