How to map NULL to No Data Time Series

Hello guys, I have a dataset with values and the values are type of decimal, but sometimes the values can be null.

So on Grafana I have this

Where in 1990 the value is null, but I would like to show it on the Time series as No Data. I can do that by mapping the value, but this is only possible if the value is a decimal to, for example if the value it’s -1 I can map it to No Data, the problem is that I can get -1 as value to, so I can’t map a specific number because it can be a real value of the dataset, so I need to map the NULL.

Is it possible?

My query

SELECT STR_TO_DATE(CONCAT(year, '-01-01'), '%Y-%m-%d') AS time, quantity
FROM database.my_table
WHERE party = 'pt'
ORDER BY time;

This is a print with -1 as “default value when it should have nothing”, and with -1 or anything that is a number I can map it

What do you mean by “show it as No Data”