fix keep alive

this reference to keep alive was missed in #12041 so chat has a
diffferent behaviour than generate

server/routes.go

@@ -1777,7 +1777,7 @@ func (s *Server) ChatHandler(c *gin.Context) {
 	}
 
 	// expire the runner
-	if len(req.Messages) == 0 && req.KeepAlive != nil && int(req.KeepAlive.Seconds()) == 0 {
+	if len(req.Messages) == 0 && req.KeepAlive != nil && req.KeepAlive.Duration == 0 {
 		s.sched.expireRunner(m)
 
 		c.JSON(http.StatusOK, api.ChatResponse{