src/Pure/PIDE/query_operation.scala

       case Some(snapshot) =>
         remove_overlay()
         reset_state()
         consume_output(Document.Snapshot.init, Command.Results.empty, Nil)
         editor.current_command(editor_context, snapshot) match {
-          case Some((command, _)) =>
+          case Some(command) =>
             current_location = Some(command)
             current_query = query
             current_status = Query_Operation.Status.WAITING
             editor.insert_overlay(command, operation_name, instance :: query)
           case None =>