Allow an empty radio button control at edit time

[altenbach]

The radio button control acts like a cluster container for booleans with some fancy logic behind it. Refactoring old code, we might have a bunch of customized booleans that we want to stick in a radiobutton control during refactoring.

For some unknown reason, we have to first drop at least one of the desired booleans into the control before we can delete the last one of the default controls that were already in there. I think we could get better work flow when doing these edits if we remove this random barrier that forces us to operate in a certain order. It would be nice if we could first empty out the radio button control and then drop all our desired customized controls in it. Of course a VI with an empty radio button control should probably be broken.

In summary, an empty radio button control should be allowed at edit time. We should be able to temporarily remove all existing content. Currently, LabVIEW won't let us remove the last remaining element if we try to do so.

(Hopefully, this is a trivial change and not something that would require lots of changes to the existing code) 😉