Fix upload error

[McTwist]

Apparently somehow it doesn't set correct slug or a file for certain Add-Ons.

Example: http://blockland.aposoc.net/categories/22

I have no idea why this happened, but apparently some error was raised and it failed to move the Add-On from temp to uploads. I will try to investigate it, but I cannot guarantee that I'll find anything that could be of help.

[McTwist]

After inspecting the error in the logs, I found out that the flashed array upload is somehow gone. I can easily write a check if that value is there, but other than that I don't know exactly what is causing this error but I at least could try to minimize the error by checking the value.