Default value needed if no data is available

[bengtner]

I find it a bit annoying wrong value (the last value) is shown if there is no data available when you hoover over a bar representing a null value. I have made a post in Home Assistant community forum about this:

https://community.home-assistant.io/t/mini-graph-card-hovering-shows-no-value/448473

A possibility to define a default value will solve this problem.

[Johnt5818]

I would also like to see a Default value defined. it would fix a problem when I am displaying Bluetooth historical data. Right now, if the Bluetooth device is offline, it spikes the graph as if it has a great signal.
Having a Default value for when the data is not there, would allow me to adjust this.

Here is my current config. The Red mark is where the Bluetooth device went offline.