Incorrect UI state when validating all files with the Validate event. 

The Upload does not pass data set in the args of its FileUploadStarting event. The values set in the args are send only for the first chunk, all chunks after that does not have that data.

This happens if the file is not first in the selected files list.

Steps to reproduce:

1. Add 2 files for upload. The first one should be bigger so you have time do to the next steps.
2. Click the Upload button. The first starts to upload.
3. Delete the second file.

When the upload process gets to the second file, a NullReferenceException is thrown.