Make RefNum controls/Indicators actually indicate something

[CoastalMaineBird]

My particular use case involves TCP Connection RefNums and Queue Refnums, but this could be applied to ALL refnums, as well.

When passing a RefNum from one VI to another, I realize it's not useful to show the numeric value on the front panel connecting control/indicator.

However, what WOULD be useful is to indicate when it's a Not-A-Refnum. 

Perhaps a red dot, or a red background, would indicate that this Refnum is Not-A-Refnum, and absence of the dot, or a plain background would indicate the opposite.