fix(cpn): crash when going into radio settings due to customisable switch groups source

[philmoz]

Fixes:

• Companion crashes when editing radio settings for radios without function switches.
• Add GRx sources to switch filter when selecting a source (color radios).

[pfeerick]

I don't think this is the complete fix... as it crashed for both radio with and without cusotmisable switches ... and still does for radios with customisable switches... e.g. TPro ;)

[pfeerick]

Thank you!... that got it. And I think that just opened up another can of worms in Companion (and possibly radio, need to check that now)... whereby model specific switches are showing up for global functions... so probably need to start working on #4333 again 🤣