Issue
When you try to refresh an embedded extract in Tableau Server, the following error occurs:java.lang.NullPointerException
More details can be found in the VizQL backgrounder logs:
VizQL error: <Timestamp> (Default,,,<SessionID>,:refresh_extracts,-) pool-21-thread-1 : ERROR com.tableausoftware.model.workgroup.service.VqlSessionService - The group with id: <ID> is no longer available and may have been deleted. This can result in a failed extract refresh if it was used as the thumbnail id.