Bad quota computation on StreamingBlob

When a Blob is used to create or update a Document, this blob may be a StreamingBlob that has a length of -1.

This case is very rare :

• no possible inside the WebUI
• no possible via Automation
• no possible via WebDav except from a MS Explorer

MS Explorer does not create the Document from the Blob.
Actually, it does create an empty document then updated it from a Stream (using WSS "put document" which calls our setStream).
In this case, in the beforeDocumentUdpate event that is used to enforce the Quota the Blob has a size of -1.