Support Float.NAN values as part of data

[johnnyzen]

It seems like Float.NaN is supported.

If I prefill a dataset with say 200 Float.NaN values, and then add valid data, nothing is drawn?

Is this as expected?

I was expecting a gap and then the data on the linechart.

[hannesa2]

Is this as expected?

No.
If you have a solution, I'm happy to merge the pull request