Added check for empty salt before attempting to encrypt password. If …

…you sign up with OAuth provider and then try to login with Email (local strategy), the Salt is empty and authentication fails.

app/models/user.js

@@ -117,6 +117,7 @@ UserSchema.methods = {
      */
     encryptPassword: function(password) {
         if (!password) return '';
+        if (!this.salt) return '';
         salt = new Buffer(this.salt, 'base64');
         return crypto.pbkdf2Sync(password, salt, 10000, 64).toString('base64');
     }