Fixed HTTP 416 error, the starting-value beyond the range!

Fixed HTTP 416 error, the starting-value beyond the range!

If the the current download-request's data has been fully downloaded, but other causes of the Operation failed (such as the inability of the incomplete temporary file copied to the target location), next, retry this download-request, the starting-value (equal to the incomplete temporary file size) will lead to out of Range!

e.g. 
Response: "Range 0-50/51" -- 51 bytes downloaded
Retry Request: "Range 51-  " -- out of range