In _uploadSingle not cleanup last ajaxAborted data

[cxgreat2014]

First click here:

if in event filepreupload I check some data (like username input is empty) and return a {message: "Please
tell me your username"}, it will show:

if user edit data then click here again, it will not do event filepreupload and show last error, because in _uploadSingle function not cleanup last ajaxAborted data.

Please fix it, thanks!