VRA 8.2 - Custom Form: Required Constraint Grayed Out

[emacintosh]

I hope I'm missing something simple here.  In Cloud Assembly, I create an input on my cloud template (blueprint).  In the corresponding custom form in Service Broker, I drag that element to the form.  But when I do, the Required field for that element under Constraints is grayed out - I can't change it from Yes. 

Am I missing something obvious here?  Or is this by design? 

My current workaround is to set a default value for that input on the blueprint.  If there is a default set there, then the Required field on the form is available again.  But I don't want a default value for these fields, I just want them to be null if not filled out. 

Thanks in advanced for any help!

[emacintosh]

It looks like adding a default with no value on the blueprint inputs does the trick too, still seems odd to me though - why is the assumed default not just null.

Edit: setting them to null actually results in the form being unable to submit.  Instead, setting them to empty strings (or equivalent for other types) works better.