Grafana show last positive value when value is 0

I have built this App that does requests to the API of Appfollow, custom exports them with Prometheus, and shows them in Grafana. I am getting stats like the average rating of an app, the average amount of reviews, and so on. Android has this problem that they delay the Information they give. For example yesterday the number of stars given for July 6 and 7 were not available. So this little box will display 0 when this is the case. Is there a way to show the last positive number as long as there is no new data above 0?