Allow line y values to be nullable

[herrrta]

I have a chart where I display a users y input for the last 90 days. They don't always provide an input for all days so I want to be able to use null y values where the data points only connect to non null values.

You can use a slope to connect a non null data point to the next non null.

[herrrta]

Currently I have my own way of doing this with non null values but it would be great if this is supported out of the box.