Fixed Mail and Snail Mail API

On a fresh install of xMail, the PHP server will give the following errors:
Notice: Undefined index: mode in C:\xampp\htdocs\xmail\mail\index.php on line 24
Notice: Undefined index: apikey in C:\xampp\htdocs\xmail\mail\index.php on line 25
Notice: Undefined index: version in C:\xampp\htdocs\xmail\mail\index.php on line 27
Notice: Undefined index: debug in C:\xampp\htdocs\xmail\mail\index.php on line 29
Notice: Undefined index: onlineMode in C:\xampp\htdocs\xmail\mail\index.php on line 30

... causing Bukkit to give errors.
This will fix that.