[omniORB] Crash on using nil reference

[Tim Ward]

From: Duncan Grisby <dgrisby@uk.research.att.com>
>
>The semantics of the reference counts are that when the count reaches
>zero, the object reference is deleted. After that, any operations on
>the object reference are dealing with freed memory, so it's impossible
>for the ORB to trap reliably. The fact that you are using _var types
>doesn't make any difference.

Ah, right. (More sophisticated smart pointers keep a map of pointers and
reference counts (in debug builds, at least), so after an object has been
deallocated the pointer can still reliably and safely spot and report this
without crashing.)

Tim Ward
Brett Ward Limited - www.brettward.co.uk