Feature Request: Labelset should return something else than an empty string if getlabel is called with a non-existent label #463

Is your feature request related to a problem? Please describe the problem.

Currently, when I use getlabel with a non-existent identifier, I get an empty string (symbol) as a response, which is not very convenient in Max.

Describe the solution you'd like to see.

In Max, it is atypical to have an empty atom (symbol/string/list). It would be more convenient to just not get anything in return (just the "getlabel"). So, currently, we get a list: ["getlabel", ""]. If it was just ["getlabel"], it would already be much more convenient to handle. But I'm open to other solutions too.

Describe alternatives you've considered

My current hack:

It works, but it would be nicer to get something easier to handle.

Additional context

This came up in the setpoint implementation for fluid.jit.plotter. Since the message can imply a new or existing identifier, I have to check if it exists in the dataset/labelset. I guess a separate contains message/method could also work, but it wouldn't be necessary if we could avoid outputting the empty symbol.