HSUploader-2: Firefox Permission Denied error

hash: d3dab59e2f8d7e9583139438d6979c9473c737c4

Fixed "Error: Permission denied to access property '0'". Firefox has trouble accessing the dataTransfer.files object with files[0]. This could be a bug on the browser or a security feature to prevent direct accessing.

Fixed by using a loop to access the FileList's iterator to retrieve the file object.