Handling added for passivated file upload and attach

When storage type repository was configured and any file type other than image was uploaded while pyIsStreamBasedUpload was set as true, uploading a file and keeping it idle for 15 minutes before clicking on attach caused pyattachInputStream to become null on the DragDropFileUpload pagelist. This caused an activityterminateException in tracer and the assignment was not submitted. This exception was due to a check in attachFile activity that calls terminateactivity when streambasedupload is true and attachinputstream is null. To resolve this, a validation rule has been added to check if the page exists, streambasedupload is true, and pyattachinputstream is null or has a value. If it is NULL, a message will be displayed about reattaching the file(s).