Empty ObjectPtr

[Andrew Sinning]

What happens if you leave an ObjectPtr with an ON DELETE CASCADE null?  
Can the entry continue to if there is no corresponding null RecId in the 
referenced table?

How about if I use a zero value?  As far as I can tell, zero is not used 
as a RecId.  Will this work?

The reason is that I have a class of objects that typically belongs to 
another object, but in some instances they will stand along, without 
relationship to the other object.

Thanks.