Update MY_Upload.php

There is a small bug if i use this html

<input type="file" name="file[1]">
<input type="file" name="file[2]">
<input type="file" name="file[3]">

With this fix everything works fine.

PS: Thanks for your work, really usefull
Merge pull request #15 from luclanet/patch-1

Update MY_Upload.php