Currently, in 1.6.0 (and probably at least since 1.4.2),
we have had a _sentinelRef used as an end-of-list marker for
the discovered list in order to avoid confusing the last object
in the discovered list with a yet-to-be-discovered object.
It's of course important that the said _sentinelRef not be
collected; so it should always be marked as a strong root.
This was not being done in the current code and should be
fixed as it might otherwise lead to hard-to-diagnose and
obscure kinds of bugs in Reference object processing.

Sub-CR's will be created as appropriate for backporting the
simple 1-line fix to older releases affected by this bug.
###@###.### 2005-04-11 18:33:22 GMT