Local surface location variables should have a value

[fahhem]

Is this a feature relevant to companion itself, and not a module?

• I believe this to be a feature for companion, not a module

Is there an existing issue for this?

• I have searched the existing issues

Describe the feature

Initially mentioned in #2733 when I thought it was a bug.

I believe the value should not be blank, as it's not currently possible in companion to distinguish between a blank variable and an unavailable variable. If a surface is not connected, the location variable is unavailable, while when it's connected it's blank. Both result in false from bool(), for instance.

Usecases

I want to show on a certain page (via the web emulator) the status of all physical devices, both via USB and satellite. I can do this for the satellite devices, as their IP addresses are non-empty but I can't do it for the USB devices.