'Null' Present at beginning of Discrete Panel


I am using the Discrete Panel Plugin (https://grafana.com/plugins/natel-discrete-panel) to map SmartThings sensor status, and at the beginning of each dataset is always ‘Null’. This does not seem to be tied to a certain time, as it is always at the beginning of the panel (far left in image).


Is there a way to filter the nulls, or have I configured the panel incorrectly? This is the query for the contact sensors:

SELECT last(“value”) FROM “contact” WHERE (“deviceName” = ‘Garage Position’) AND timeFilter GROUP BY time(__interval) fill(previous)

The null values are due to the fact that the previous switchtpoint is not in the selected time frame.
To solve this I update every 10 minutes the status of my switch in the influxdb.

Kind regards