Fix NaN-NaN... in dates

lib/abstract-class.js

@@ -308,7 +308,6 @@ AbstractClass.prototype.propertyChanged = function (attr) {
     return this['_' + attr] !== this[attr + '_was'];
 };
 
-
 AbstractClass.prototype.reload = function (cb) {
     this.constructor.find(this.id, cb);
 };

lib/adapters/mysql.js

@@ -76,6 +76,7 @@ MySQL.prototype.toDatabase = function (prop, val) {
     if (prop.type.name === 'Number') return val;
     if (val === null) return 'NULL';
     if (prop.type.name === 'Date') {
+        if (!val) return 'NULL';
         if (!val.toUTCString) {
             val = new Date(val);
         }